diff --git a/R/create_chatlog.R b/R/create_chatlog.R
index d307525..b69bd2b 100644
--- a/R/create_chatlog.R
+++ b/R/create_chatlog.R
@@ -13,8 +13,8 @@
 #' @param n_diff_smilies Number of different smilies that are used in the simulated chat.
 #' @param n_media Number of messages that contain omitted media files. Must be smaller or equal to n_messages.
 #' @param n_sdp Number of messages that contain self-deleting photos. Must be smaller or equal to n_messages.
-#' @param startdate Earliest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate.
-#' @param enddate Latest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate.
+#' @param startdate Earliest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate. Input is interpreted as UTC
+#' @param enddate Latest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate. Input is interpreted as UTC
 #' @param language Parameter for the language setting of the exporting phone. Influences structure of system messages
 #' @param time_format Parameter for the time format setting of the exporting phone (am/pm vs. 24h). Influences the structure of timestamps.
 #' @param os Parameter for the operating system setting of the exporting phone. Influences the structure of timestamps and WhatsApp system messages.
@@ -87,20 +87,20 @@ create_chatlog <- function(n_messages = 150,
   }
 
   # validating startdate
-  startdate_check <- try(as.Date(startdate, format = "%d.%m.%Y"))
+  startdate_check <- try(as.Date(startdate, format = "%d.%m.%Y", tz = "UTC"))
   if ("try-error" %in% class(startdate_check) || is.na(startdate_check)) {
     print("Variable 'startdate' musst be a character string of format dd.mm.YYYY")
   }
 
   # validating enddate
-  enddate_check <- try(as.Date(enddate, format = "%d.%m.%Y"))
+  enddate_check <- try(as.Date(enddate, format = "%d.%m.%Y", tz = "UTC"))
   if ("try-error" %in% class(enddate_check) || is.na(enddate_check)) {
     print("Variable 'enddate' musst be a character string of format dd.mm.YYYY")
   }
 
   # validate that startdate is before enddate
-  sDate <- as.POSIXct(as.Date(startdate, format = "%d.%m.%Y"))
-  eDate <- as.POSIXct(as.Date(enddate, format = "%d.%m.%Y"))
+  sDate <- as.POSIXct(as.Date(startdate, format = "%d.%m.%Y", tz = "UTC"), tz = "UTC")
+  eDate <- as.POSIXct(as.Date(enddate, format = "%d.%m.%Y", tz = "UTC"), tz = "UTC")
 
   if (sDate >= eDate) {
     warning("starting date must be earlier than ending date.")
@@ -172,8 +172,8 @@ create_chatlog <- function(n_messages = 150,
 
   # Timestamp function (taken from: https://stackoverflow.com/questions/42021394/random-incremental-timestamp-in-r)
   RandomTimeStamp <- function(M, sDate = startdate, eDate = enddate) {
-    sDate <- as.POSIXct(as.Date(sDate, format = "%d.%m.%Y"))
-    eDate <- as.POSIXct(as.Date(eDate, format = "%d.%m.%Y"))
+    sDate <- as.POSIXct(as.Date(sDate, format = "%d.%m.%Y", tz = "UTC"), tz = "UTC")
+    eDate <- as.POSIXct(as.Date(eDate, format = "%d.%m.%Y", tz = "UTC"), tz = "UTC")
     dTime <- as.numeric(difftime(eDate, sDate, units = "sec"))
     sTimeStamp <- sort(runif(M, 0, dTime))
     TimeStamp <- sDate + sTimeStamp
@@ -188,29 +188,29 @@ create_chatlog <- function(n_messages = 150,
   if (language == "german") {
     if (os == "android") {
       if (time_format == "24h") {
-        ts <- strftime(ts, format = "%d.%m.%y, %H:%M - ")
+        ts <- strftime(ts, format = "%d.%m.%y, %H:%M - ", tz = "UTC")
       } else {
-        ts <- strftime(ts, format = "%d.%m.%y, %I:%M %p - ")
+        ts <- strftime(ts, format = "%d.%m.%y, %I:%M %p - ", tz = "UTC")
       }
     } else {
       if (time_format == "24h") {
-        ts <- strftime(ts, format = "[%d.%m.%y, %H:%M:%S] ")
+        ts <- strftime(ts, format = "[%d.%m.%y, %H:%M:%S] ", tz = "UTC")
       } else {
-        ts <- strftime(ts, format = "[%m/%d/%y, %I:%M:%S %p] ")
+        ts <- strftime(ts, format = "[%m/%d/%y, %I:%M:%S %p] ", tz = "UTC")
       }
     }
   } else {
     if (os == "android") {
       if (time_format == "24h") {
-        ts <- strftime(ts, format = "%m/%d/%y, %H:%M - ")
+        ts <- strftime(ts, format = "%m/%d/%y, %H:%M - ", tz = "UTC")
       } else {
-        ts <- strftime(ts, format = "%m/%d/%y, %I:%M %p - ")
+        ts <- strftime(ts, format = "%m/%d/%y, %I:%M %p - ", tz = "UTC")
       }
     } else {
       if (time_format == "24h") {
-        ts <- strftime(ts, format = "[%m/%d/%y, %H:%M:%S] ")
+        ts <- strftime(ts, format = "[%m/%d/%y, %H:%M:%S] ", tz = "UTC")
       } else {
-        ts <- strftime(ts, format = "[%m/%d/%y, %I:%M:%S %p] ")
+        ts <- strftime(ts, format = "[%m/%d/%y, %I:%M:%S %p] ", tz = "UTC")
       }
     }
   }
diff --git a/R/plot_emoji.R b/R/plot_emoji.R
index 4c03d2f..e433b1b 100644
--- a/R/plot_emoji.R
+++ b/R/plot_emoji.R
@@ -2,8 +2,8 @@
 #' @description Plots four different types of graphs for the emoji contained in a parsed WhatsApp chat log. Returns dataframe used for plotting if desired.
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param min_occur Minimum number of occurrences for emoji to be included in the plots. Default is 1.
 #' @param return_data If TRUE, returns the subsetted data frame used for plotting. Default is FALSE.
 #' @param emoji_vec A vector of emoji that the visualizations and data will be restricted to.
@@ -29,7 +29,7 @@
 plot_emoji <- function(data,
                        names = "all",
                        starttime = "1960-01-01 00:00",
-                       endtime = as.character(Sys.time()),
+                       endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                        min_occur = 1,
                        return_data = FALSE,
                        emoji_vec = "all",
@@ -43,10 +43,14 @@ plot_emoji <- function(data,
   Date <- Sender <- day <- hour <- `Number of Emoji` <- ave <- total <- Var1 <- Freq <- n <- emoji <- Emoji <- Glyph <-  NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # min_occur needs to be 1 or bigger
   if (min_occur < 1) stop("Please provide a min_occur of >= 1.")
@@ -70,17 +74,17 @@ plot_emoji <- function(data,
   Dictionary <- read.csv(system.file("EmojiDictionary.csv", package = "WhatsR"))
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -140,16 +144,17 @@ plot_emoji <- function(data,
 
   }
 
-  NewDates <- as.POSIXct(unlist(NewDates),origin = '1970-01-01')
+  NewDates <- as.POSIXct(unlist(NewDates),origin = '1970-01-01', tz="UTC")
 
   # pasting together
   options(stringsAsFactors = FALSE)
   NewFrame <- cbind.data.frame(NewDates,NewSender,NewEmoji)
 
   # creating time data
-  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates)$hour
-  NewFrame$year <- as.POSIXlt(NewFrame$NewDates)$year + 1900
-  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates), abbreviate = FALSE)
+  # TODO: Maybe this is where it goes wrong?
+  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$hour
+  NewFrame$year <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$year + 1900
+  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates,tz = "UTC"), abbreviate = FALSE)
 
   # setting correct emoji_vec
   if (length(emoji_vec) == 1 && emoji_vec == "all") {
@@ -180,7 +185,7 @@ plot_emoji <- function(data,
     # factor ordering
     weekdays <- rev(c("Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"))
 
-    # transalte to english for better compatibility
+    # translate to english for better compatibility
     helperframe2$day <- mgsub(helperframe2$day,
                               pattern = c("Sonntag","Samstag","Freitag","Donnerstag","Mittwoch","Dienstag","Montag"),
                               replacement = weekdays)
diff --git a/R/plot_lexical_dispersion.R b/R/plot_lexical_dispersion.R
index f72a044..fff9786 100644
--- a/R/plot_lexical_dispersion.R
+++ b/R/plot_lexical_dispersion.R
@@ -2,8 +2,8 @@
 #' @description Visualizes the occurrence of specific keywords within the chat. Requires the raw message content to be contained in the preprocessed data
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}} using anonimize = FALSE or anonimize = "add".
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param keywords A vector of keywords to be displayed, default is c("hello","world").
 #' @param return_data Default is FALSE, returns data frame used for plotting when TRUE.
 #' @param exclude_sm If TRUE, excludes the WhatsApp System Messages from the descriptive statistics. Default is FALSE.
@@ -23,17 +23,21 @@
 plot_lexical_dispersion <- function(data,
                                     names = "all",
                                     starttime = "1960-01-01 00:00",
-                                    endtime = as.character(Sys.time()),
+                                    endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                                     keywords = c("hello", "world"),
                                     return_data = FALSE,
                                     exclude_sm = FALSE,
                                     ...) {
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # Mesage column must be contained
   if (!is.character(data$Flat)) {stop("'data' must contain a character column named 'Message'")}
@@ -58,17 +62,17 @@ plot_lexical_dispersion <- function(data,
   keywords <- tolower(keywords)
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/plot_links.R b/R/plot_links.R
index acc800e..715b982 100644
--- a/R/plot_links.R
+++ b/R/plot_links.R
@@ -2,8 +2,8 @@
 #' @description Visualizes the occurrence of links in a WhatsApp chatlog
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param use_domains If TRUE, links are shortened to domains. This includes the inputs in link_vec. Default is TRUE.
 #' @param exclude_long Either NA or a numeric value. If numeric value is provided, removes all links/domains longer than x characters. Default is 50.
 #' @param min_occur The minimum number of occurrences a link has to have to be included in the visualization. Default is 1.
@@ -28,7 +28,7 @@
 plot_links <- function(data,
                        names = "all",
                        starttime = "1960-01-01 00:00",
-                       endtime = as.character(Sys.time()),
+                       endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                        use_domains = TRUE,
                        exclude_long = 50,
                        min_occur = 1,
@@ -41,10 +41,14 @@ plot_links <- function(data,
   Date <- Sender <- Links <- URL <- day <- hour <- n <- `Number of Links` <- ave <- total <- Var1 <- Freq <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # min_occur must be >= 1
   if (min_occur < 1) stop("Please provide a min_occur of >= 1.")
@@ -89,17 +93,17 @@ plot_links <- function(data,
   options(dplyr.summarise.inform = FALSE)
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -151,7 +155,7 @@ plot_links <- function(data,
     NewDates[[i]] <- rep(data$DateTime[i], NoElements[i])
   }
 
-  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01")
+  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01",tz = "UTC")
 
   # shorten URLs to domain
   if (use_domains == TRUE) {
@@ -166,9 +170,9 @@ plot_links <- function(data,
   NewFrame <- cbind.data.frame(NewDates, NewSender, NewUrls)
 
   # creating time data
-  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates)$hour
-  NewFrame$year <- as.POSIXlt(NewFrame$NewDates)$year + 1900
-  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates), abbreviate = FALSE)
+  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$hour
+  NewFrame$year <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$year + 1900
+  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates,tz = "UTC"), abbreviate = FALSE)
 
   # setting correct link_vec
   if (length(link_vec) == 1 && link_vec == "all") {
diff --git a/R/plot_locations.R b/R/plot_locations.R
index d876008..2380ed9 100644
--- a/R/plot_locations.R
+++ b/R/plot_locations.R
@@ -2,8 +2,8 @@
 #' @description Plots the location data that is sent in the WhatsApp chatlog on an auto-scaled map. Requires unanonimized 'Location' column in data
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}}with anonimize= FALSE or anonimize = "add".
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param mapzoom Value for zoom into the map passed down to \code{\link[ggmap]{get_map}}. Default value is 5. Higher zoom will auto-download more map files which can take a while.
 #' @param return_data If TRUE, returns a data frame of LatLon coordinates extracted from the chat for more elaborate plotting. Default is FALSE.
 #' @param jitter_value Amount of random jitter to add to the geolocations to hide exact locations. Default value is 0.01. Can be NA for exact locations.
@@ -30,7 +30,7 @@
 plot_locations <- function(data,
                            names = "all",
                            starttime = "1960-01-01 00:00",
-                           endtime = as.character(Sys.time()),
+                           endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                            mapzoom = 5,
                            return_data = FALSE,
                            jitter_value = 0.01,
@@ -44,10 +44,14 @@ plot_locations <- function(data,
   Lon <- Lat <- Sender <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # jitter_value checks
   if (!(is.numeric(jitter_value) | is.na(jitter_value))) {stop("jitter_value must be either NA for exact location or a numeric value > 0")}
@@ -60,17 +64,17 @@ plot_locations <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/plot_media.R b/R/plot_media.R
index 26f87c8..7525187 100644
--- a/R/plot_media.R
+++ b/R/plot_media.R
@@ -2,8 +2,8 @@
 #' @description Creates summary data frames or visualizations of sent media files or file types
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}} and was exported usng the "with media" option.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param use_filetype If TRUE, shortens sent file attachments to file types.
 #' @param min_occur The minimum number of occurrences a media (type) has to have to be included in the visualization. Default is 1.
 #' @param return_data If TRUE, returns the subset data frame. Default is FALSE.
@@ -27,7 +27,7 @@
 plot_media <- function(data,
                        names = "all",
                        starttime = "1960-01-01 00:00",
-                       endtime = as.character(Sys.time()),
+                       endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                        use_filetype = TRUE,
                        min_occur = 1,
                        return_data = FALSE,
@@ -48,10 +48,14 @@ plot_media <- function(data,
     }
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # min_occur must be >= 1
   if (min_occur < 1) stop("Please provide a min_occur of >= 1.")
@@ -72,17 +76,17 @@ plot_media <- function(data,
   if (!is.logical(use_filetype)) stop("use_filetype has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -133,16 +137,16 @@ plot_media <- function(data,
     NewDates[[i]] <- rep(data$DateTime[i], NoElements[i])
   }
 
-  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01")
+  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01",tz="UTC")
 
   # pasting together
   options(stringsAsFactors = FALSE)
   NewFrame <- cbind.data.frame(NewDates, NewSender, NewMedia)
 
   # creating time data
-  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates)$hour
-  NewFrame$year <- as.POSIXlt(NewFrame$NewDates)$year + 1900
-  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates), abbreviate = FALSE)
+  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$hour
+  NewFrame$year <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$year + 1900
+  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates,tz = "UTC"), abbreviate = FALSE)
 
   # setting correct media_vec
   if (length(media_vec) == 1 && media_vec == "all") {
diff --git a/R/plot_messages.R b/R/plot_messages.R
index 8f93f2d..638736f 100644
--- a/R/plot_messages.R
+++ b/R/plot_messages.R
@@ -2,8 +2,8 @@
 #' @description Plots summarizing the amount of messages per person
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param plot Type of plot to be returned, options are "bar", "cumsum", "heatmap" and "pie". Default is "bar".
 #' @param return_data If TRUE, returns the subset data frame. Default is FALSE.
 #' @param exclude_sm If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.
@@ -24,7 +24,7 @@
 plot_messages <- function(data,
                           names = "all",
                           starttime = "1960-01-01 00:00",
-                          endtime = as.character(Sys.time()),
+                          endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                           plot = "bar",
                           return_data = FALSE,
                           exclude_sm = FALSE) {
@@ -33,10 +33,14 @@ plot_messages <- function(data,
   Var1 <- Freq <- DateTime <- total <- Sender <- day <- hour <- `Number of Messages` <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # return_data must be bool
   if (!is.logical(return_data)) stop("return_data has to be either TRUE or FALSE.")
@@ -48,17 +52,17 @@ plot_messages <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -152,9 +156,9 @@ plot_messages <- function(data,
     # creating time data
     data <- cbind(data, MessageCount = rep(1, dim(data)[1]))
     NewFrame <- data[, c("DateTime", "Sender", "MessageCount")]
-    NewFrame$hour <- as.POSIXlt(NewFrame$DateTime)$hour
-    NewFrame$year <- as.POSIXlt(NewFrame$DateTime)$year + 1900
-    NewFrame$day <- weekdays(as.POSIXlt(NewFrame$DateTime), abbreviate = FALSE)
+    NewFrame$hour <- as.POSIXlt(NewFrame$DateTime,tz="UTC")$hour
+    NewFrame$year <- as.POSIXlt(NewFrame$DateTime,tz="UTC")$year + 1900
+    NewFrame$day <- weekdays(as.POSIXlt(NewFrame$DateTime,tz="UTC"), abbreviate = FALSE)
 
     # shaping dataframe
     helperframe2 <- NewFrame %>%
diff --git a/R/plot_network.R b/R/plot_network.R
index c2616ec..5854381 100644
--- a/R/plot_network.R
+++ b/R/plot_network.R
@@ -2,8 +2,8 @@
 #' @description Plots a network for replies between authors in chat logs. Each message is evaluated as a reply to the previous one.
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the visualization will be restricted to. Non-listed authors will be removed.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Input is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Input is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param return_data If TRUE, returns a data frame of subsequent interactions with senders and recipients. Default is FALSE.
 #' @param collapse_sessions Whether multiple subsequent messages by the same sender should be collapsed into one row. Default is FALSE.
 #' @param edgetype What type of content is displayed as an edge. Must be one of "TokCount","EmojiCount","SmilieCount","LocationCount","URLCount","MediaCount" or "n".
@@ -26,7 +26,7 @@
 plot_network <- function(data,
                          names = "all",
                          starttime = "1960-01-01 00:00",
-                         endtime = as.character(Sys.time()),
+                         endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                          return_data = FALSE,
                          collapse_sessions = FALSE,
                          edgetype = "n",
@@ -36,10 +36,14 @@ plot_network <- function(data,
   mutate <- trials <- start <- streak_id <- ungroup <- `draw_network` <- `.` <- `get_streaks` <- `%v%<-` <- `lagged` <- `lag` <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # return_data must be bool
   if (!is.logical(return_data)) stop("return_data has to be either TRUE or FALSE.")
@@ -54,17 +58,17 @@ plot_network <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -155,10 +159,10 @@ plot_network <- function(data,
 
     # computing aggregate counts of tokens, smilies, emoji etc
 
-    # taken form: https://www.r-bloggers.com/2020/06/detecting-streaks-in-r/
+    # source: https://www.r-bloggers.com/2020/06/detecting-streaks-in-r/
     get_streaks <- function(vec) {
       x <- data.frame(trials = vec)
-      x <- x %>% mutate(lagged = lag(trials)) %>% # note: that's dplyr::lag, not stats::lag
+      x <- x %>% mutate(lagged = lag(trials)) %>%
         mutate(start = (trials != lagged))
       x[1, "start"] <- TRUE
       x <- x %>% mutate(streak_id = cumsum(start))
@@ -246,6 +250,7 @@ plot_network <- function(data,
 
     # combining into dataset
     # TODO: Error in `data.frame(..., check.names = FALSE)`: arguments imply differing number of rows: 1, 34 [only occurs in testing, not in use]
+    # possibly an issue with locale, timezone etc?
     NetFrame <- cbind.data.frame(
       Sender,
       AnsweredTo,
diff --git a/R/plot_replytimes.R b/R/plot_replytimes.R
index b22aef2..8b32f5d 100644
--- a/R/plot_replytimes.R
+++ b/R/plot_replytimes.R
@@ -2,8 +2,8 @@
 #' @description Visualizes the reply times and reaction times to messages per author
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param return_data If TRUE, returns a data frame of response times extracted from the chat for more elaborate plotting. Default is FALSE.
 #' @param aggregate_sessions If TRUE, concurrent messages of the same author are aggregated into one session. Default is TRUE.
 #' @param plot Type of plot to be returned, options are "box" and "heatmap".
@@ -30,7 +30,7 @@
 plot_replytimes <- function(data,
                             names = "all",
                             starttime = "1960-01-01 00:00",
-                            endtime = as.character(Sys.time()),
+                            endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                             return_data = FALSE,
                             aggregate_sessions = TRUE,
                             plot = "box",
@@ -41,10 +41,14 @@ plot_replytimes <- function(data,
   `.` <- Sender <- ReactionTime <- day <- hour <- median <- `Median Reply time` <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # return_data must be bool
   if (!is.logical(return_data)) stop("'return_data' has to be either TRUE or FALSE.")
@@ -62,17 +66,17 @@ plot_replytimes <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/plot_smilies.R b/R/plot_smilies.R
index b8ed9ca..cc3eec8 100644
--- a/R/plot_smilies.R
+++ b/R/plot_smilies.R
@@ -2,8 +2,8 @@
 #' @description Plots the smilies used in WhatsApp chat logs by sender
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param min_occur The minimum number of occurrences a smiley has to have to be included in the visualization. Default is 1.
 #' @param return_data If TRUE, returns a data frame of smilies extracted from the chat for more elaborate plotting. Default is FALSE.
 #' @param smilie_vec A vector of smilies that the visualizations will be restricted to.
@@ -22,7 +22,7 @@
 plot_smilies <- function(data,
                          names = "all",
                          starttime = "1960-01-01 00:00",
-                         endtime = as.character(Sys.time()),
+                         endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                          min_occur = 1,
                          return_data = FALSE,
                          smilie_vec = "all",
@@ -33,10 +33,14 @@ plot_smilies <- function(data,
   day <- hour <- n <- `Number of Smilies` <- ave <- total <- Var1 <- Freq <- n <- DateTime <- Total <- Sender <- Smilies <- Amount <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # min_occur must be >= 1
   if (min_occur < 1) stop("Please provide a 'min_occur' of >= 1.")
@@ -54,17 +58,17 @@ plot_smilies <- function(data,
   if (!is.logical(exclude_sm)) stop("'exclude_sm' has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -115,16 +119,16 @@ plot_smilies <- function(data,
     NewDates[[i]] <- rep(data$DateTime[i], NoElements[i])
   }
 
-  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01")
+  NewDates <- as.POSIXct(unlist(NewDates), origin = "1970-01-01",tz="UTC")
 
   # pasting together
   options(stringsAsFactors = FALSE)
   NewFrame <- cbind.data.frame(NewDates, NewSender, NewSmilies)
 
   # creating time data
-  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates)$hour
-  NewFrame$year <- as.POSIXlt(NewFrame$NewDates)$year + 1900
-  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates), abbreviate = FALSE)
+  NewFrame$hour <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$hour
+  NewFrame$year <- as.POSIXlt(NewFrame$NewDates,tz = "UTC")$year + 1900
+  NewFrame$day <- weekdays(as.POSIXlt(NewFrame$NewDates,tz = "UTC"), abbreviate = FALSE)
 
   # setting correct smilie_vec
   if (length(smilie_vec) == 1 && smilie_vec == "all") {
diff --git a/R/plot_tokens.R b/R/plot_tokens.R
index c12cab7..e9386d4 100644
--- a/R/plot_tokens.R
+++ b/R/plot_tokens.R
@@ -2,8 +2,8 @@
 #' @description Visualizing token distribution per person
 #' @param data A WhatsApp chatlog that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param plot The type of plot to be used. Options include "bar","box","violin" and "cumsum". Default is "bar".
 #' @param return_data If TRUE, returns the subsetted data frame. Default is FALSE.
 #' @param exclude_sm If TRUE, excludes the WhatsApp System Messages from the descriptive statistics. Default is FALSE.
@@ -23,7 +23,7 @@
 plot_tokens <- function(data,
                         names = "all",
                         starttime = "1960-01-01 00:00",
-                        endtime = as.character(Sys.time()),
+                        endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                         plot = "bar",
                         return_data = FALSE,
                         exclude_sm = FALSE) {
@@ -32,10 +32,14 @@ plot_tokens <- function(data,
   tokens <- freq <- word <- Sender <- TokCount <- DateTime <- total <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # return_data must be bool
   if (!is.logical(return_data)) stop("'return_data' has to be either TRUE or FALSE.")
@@ -47,17 +51,17 @@ plot_tokens <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")#
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/plot_tokens_over_time.R b/R/plot_tokens_over_time.R
index 974c54f..cce27ef 100644
--- a/R/plot_tokens_over_time.R
+++ b/R/plot_tokens_over_time.R
@@ -3,8 +3,8 @@
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}} with parameters anonimize = FALSE or anonimize = "add".
 #' @param names A vector of author names that the plots will be restricted to.
 #' @param names_col A column indicated by a string that should be accessed to determine the names. Only needs to be changed when \code{\link[WhatsR]{parse_chat}} used the parameter anon = "add" and the column "Anonymous" should be used. Default is "Sender".
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param plot Type of plot to be returned. Options are "year", "day", "hour", "heatmap" and "alltime". Default is "alltime".
 #' @param return_data If TRUE, returns the subset data frame. Default is FALSE.
 #' @param exclude_sm If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.
@@ -25,7 +25,7 @@ plot_tokens_over_time <- function(data,
                                   names = "all",
                                   names_col = "Sender",
                                   starttime = "1960-01-01 00:00",
-                                  endtime = as.character(Sys.time()),
+                                  endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                                   plot = "alltime",
                                   return_data = FALSE,
                                   exclude_sm = FALSE) {
@@ -34,10 +34,14 @@ plot_tokens_over_time <- function(data,
   DateTime <- TokCount <- Sender <- year <- day <- hour <- `Number of Tokens` <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # return_data must be bool
   if (!is.logical(return_data)) stop("'return_data' has to be either TRUE or FALSE.")
@@ -49,17 +53,17 @@ plot_tokens_over_time <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
@@ -85,9 +89,9 @@ plot_tokens_over_time <- function(data,
   helperframe <- data[, c("DateTime", "Sender", "TokCount")]
 
   # creating time data
-  helperframe$hour <- as.POSIXlt(helperframe$DateTime)$hour
-  helperframe$year <- as.POSIXlt(helperframe$DateTime)$year + 1900
-  helperframe$day <- weekdays(as.POSIXlt(helperframe$DateTime), abbreviate = FALSE)
+  helperframe$hour <- as.POSIXlt(helperframe$DateTime,tz="UTC")$hour
+  helperframe$year <- as.POSIXlt(helperframe$DateTime,tz="UTC")$year + 1900
+  helperframe$day <- weekdays(as.POSIXlt(helperframe$DateTime,tz="UTC"), abbreviate = FALSE)
 
   # basic barchart
   if (plot == "alltime") {
diff --git a/R/plot_wordcloud.R b/R/plot_wordcloud.R
index b3c9fea..231ce5a 100644
--- a/R/plot_wordcloud.R
+++ b/R/plot_wordcloud.R
@@ -2,8 +2,8 @@
 #' @description Creates a wordcloud by author for WhatsApp chat logs. Requires raw message text to be present in data.
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}} and anonimize = FALSE or anonimize = "add"
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param stop The language for stopword removal. Stopwords are taken from \code{\link[tm]{stopwords}}. Options are "english" and "german".
 #' @param comparison Must be TRUE or FALSE. If TRUE, will split up wordcloud by sender. Default is FALSE.
 #' @param return_data Will return the data frame used to create the plot if TRUE. Default is FALSE.
@@ -26,7 +26,7 @@
 plot_wordcloud <- function(data,
                            names = "all",
                            starttime = "1960-01-01 00:00",
-                           endtime = as.character(Sys.time()),
+                           endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                            remove_stops = TRUE,
                            stop = "english",
                            comparison = FALSE,
@@ -39,10 +39,14 @@ plot_wordcloud <- function(data,
   `tokens` <- `freq` <- `word` <- NULL
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # font_size must be >= 1
   if (font_size < 1) stop("Please provide a 'font_size' of >= 1.")
@@ -69,17 +73,17 @@ plot_wordcloud <- function(data,
   tm_stopwords <- readRDS(system.file("tm_stopwords.rds", package = "WhatsR"))
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime, asUTC = TRUE))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/summarize_chat.R b/R/summarize_chat.R
index bf566ac..dcb18cd 100644
--- a/R/summarize_chat.R
+++ b/R/summarize_chat.R
@@ -26,6 +26,10 @@
 summarize_chat <- function(data, exclude_sm = FALSE) {
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # exclude_sm must be bool
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
diff --git a/R/summarize_tokens_per_person.R b/R/summarize_tokens_per_person.R
index 9d3725b..af59e3e 100644
--- a/R/summarize_tokens_per_person.R
+++ b/R/summarize_tokens_per_person.R
@@ -2,8 +2,8 @@
 #' @description Summarizing the distribution of tokens for sent messages
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of author names that the plots will be restricted to.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param exclude_sm If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.
 #' @importFrom anytime anytime
 #' @export
@@ -16,14 +16,18 @@
 summarize_tokens_per_person <- function(data,
                                         names = "all",
                                         starttime = "1960-01-01 00:00",
-                                        endtime = as.character(Sys.time()),
+                                        endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                                         exclude_sm = FALSE) {
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # names in data or all names
   if (!("all" %in% names) & any(!names %in% data$Sender)) stop("names has to either be \"all\" or a vector of names to include.")
@@ -32,17 +36,17 @@ summarize_tokens_per_person <- function(data,
   if (!is.logical(exclude_sm)) stop("excludeSM has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime, asUTC = TRUE)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(data$DateTime)
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime, asUTC = TRUE)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/R/tailor_chat.R b/R/tailor_chat.R
index 6e08ef4..7b2affb 100644
--- a/R/tailor_chat.R
+++ b/R/tailor_chat.R
@@ -2,8 +2,8 @@
 #' @description Excluding parts of the chat by senders or timestamps
 #' @param data A WhatsApp chat log that was parsed with \code{\link[WhatsR]{parse_chat}}.
 #' @param names A vector of names that the output is restricted to. Messages from other non-contained authors are excluded.
-#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
-#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".
+#' @param starttime Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
+#' @param endtime Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.
 #' @param exclude_sm If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.
 #' @importFrom anytime anytime
 #' @export
@@ -16,14 +16,18 @@
 tailor_chat <- function(data,
                         names = "all",
                         starttime = "1960-01-01 00:00",
-                        endtime = as.character(Sys.time()),
+                        endtime = as.character(as.POSIXct(Sys.time(),tz = "UTC")),
                         exclude_sm = FALSE) {
 
   # catching bad params
+
+  # checking data
+  if(!is.data.frame(data)){stop("'data' must be a dataframe parsed with parse_chat()")}
+
   # start- and endtime are convertable to POSIXct
-  if (is.character(starttime) == FALSE | is.na(anytime(starttime))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (is.character(endtime) == FALSE | is.na(anytime(endtime))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
-  if (anytime(starttime) >= anytime(endtime)) stop("starttime has to be before endtime.")
+  if (is.character(starttime) == FALSE | is.na(anytime(starttime, asUTC=TRUE,tz="UTC"))) stop("starttime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (is.character(endtime) == FALSE | is.na(anytime(endtime, asUTC=TRUE,tz="UTC"))) stop("endtime has to be a character string in the form of 'yyyy-mm-dd hh:mm' that can be converted by anytime().")
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") >= anytime(endtime, asUTC=TRUE,tz="UTC")) stop("starttime has to be before endtime.")
 
   # names in data or all names
   if (!("all" %in% names) & any(!names %in% data$Sender)) stop("names has to either be \"all\" or a vector of names to include.")
@@ -32,17 +36,17 @@ tailor_chat <- function(data,
   if (!is.logical(exclude_sm)) stop("exclude_sm has to be either TRUE or FALSE.")
 
   # setting starttime
-  if (starttime == anytime("1960-01-01 00:00")) {
-    starttime <- min(anytime(data$DateTime))
+  if (anytime(starttime, asUTC=TRUE,tz="UTC") <= min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    starttime <- min(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    starttime <- anytime(starttime)
+    starttime <- anytime(starttime, asUTC=TRUE,tz="UTC")
   }
 
   # setting endtime
-  if (difftime(Sys.time(), endtime, units = "min") < 1) {
-    endtime <- max(anytime(data$DateTime))
+  if (anytime(endtime, asUTC=TRUE,tz="UTC") >= max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))) {
+    endtime <- max(anytime(data$DateTime, asUTC=TRUE,tz="UTC"))
   } else {
-    endtime <- anytime(endtime)
+    endtime <- anytime(endtime, asUTC=TRUE,tz="UTC")
   }
 
   # setting names argument
diff --git a/inst/TailoredData2.rds b/inst/TailoredData2.rds
index dc5140c..abab0bd 100644
Binary files a/inst/TailoredData2.rds and b/inst/TailoredData2.rds differ
diff --git a/inst/TailoredData3.rds b/inst/TailoredData3.rds
index ed3fc96..0a625b7 100644
Binary files a/inst/TailoredData3.rds and b/inst/TailoredData3.rds differ
diff --git a/inst/test_emoji2.rds b/inst/test_emoji2.rds
index bbceb85..6a6565c 100644
Binary files a/inst/test_emoji2.rds and b/inst/test_emoji2.rds differ
diff --git a/inst/test_emoji3.rds b/inst/test_emoji3.rds
index ed686f4..8b2bbed 100644
Binary files a/inst/test_emoji3.rds and b/inst/test_emoji3.rds differ
diff --git a/inst/test_links2.rds b/inst/test_links2.rds
index c5c828b..5b121e0 100644
Binary files a/inst/test_links2.rds and b/inst/test_links2.rds differ
diff --git a/inst/test_links3.rds b/inst/test_links3.rds
index c100301..14e92c3 100644
Binary files a/inst/test_links3.rds and b/inst/test_links3.rds differ
diff --git a/inst/test_media1.rds b/inst/test_media1.rds
index fd0c772..c0f5aef 100644
Binary files a/inst/test_media1.rds and b/inst/test_media1.rds differ
diff --git a/inst/test_media3.rds b/inst/test_media3.rds
index 05839b3..8877a1c 100644
Binary files a/inst/test_media3.rds and b/inst/test_media3.rds differ
diff --git a/inst/test_smilies3.rds b/inst/test_smilies3.rds
index db42963..5ebb5b2 100644
Binary files a/inst/test_smilies3.rds and b/inst/test_smilies3.rds differ
diff --git a/inst/test_smilies4.rds b/inst/test_smilies4.rds
index e620b72..e017a2e 100644
Binary files a/inst/test_smilies4.rds and b/inst/test_smilies4.rds differ
diff --git a/man/create_chatlog.Rd b/man/create_chatlog.Rd
index 64f3140..e047c13 100644
--- a/man/create_chatlog.Rd
+++ b/man/create_chatlog.Rd
@@ -45,9 +45,9 @@ create_chatlog(
 
 \item{n_sdp}{Number of messages that contain self-deleting photos. Must be smaller or equal to n_messages.}
 
-\item{startdate}{Earliest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate.}
+\item{startdate}{Earliest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate. Input is interpreted as UTC}
 
-\item{enddate}{Latest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate.}
+\item{enddate}{Latest possible date for messages. Format is 'dd.mm.yyyy'. Timestamps for messages are created automatically between startdate and enddate. Input is interpreted as UTC}
 
 \item{language}{Parameter for the language setting of the exporting phone. Influences structure of system messages}
 
diff --git a/man/figures/2.png b/man/figures/2.png
deleted file mode 100644
index 9ca9dbb..0000000
Binary files a/man/figures/2.png and /dev/null differ
diff --git a/man/plot_emoji.Rd b/man/plot_emoji.Rd
index bedae8f..38c2ad2 100644
--- a/man/plot_emoji.Rd
+++ b/man/plot_emoji.Rd
@@ -8,7 +8,7 @@ plot_emoji(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   min_occur = 1,
   return_data = FALSE,
   emoji_vec = "all",
@@ -23,9 +23,9 @@ plot_emoji(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{min_occur}{Minimum number of occurrences for emoji to be included in the plots. Default is 1.}
 
diff --git a/man/plot_lexical_dispersion.Rd b/man/plot_lexical_dispersion.Rd
index d2a8ff0..e0fb920 100644
--- a/man/plot_lexical_dispersion.Rd
+++ b/man/plot_lexical_dispersion.Rd
@@ -8,7 +8,7 @@ plot_lexical_dispersion(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   keywords = c("hello", "world"),
   return_data = FALSE,
   exclude_sm = FALSE,
@@ -20,9 +20,9 @@ plot_lexical_dispersion(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{keywords}{A vector of keywords to be displayed, default is c("hello","world").}
 
diff --git a/man/plot_links.Rd b/man/plot_links.Rd
index 6920a84..4dd95ab 100644
--- a/man/plot_links.Rd
+++ b/man/plot_links.Rd
@@ -8,7 +8,7 @@ plot_links(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   use_domains = TRUE,
   exclude_long = 50,
   min_occur = 1,
@@ -23,9 +23,9 @@ plot_links(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{use_domains}{If TRUE, links are shortened to domains. This includes the inputs in link_vec. Default is TRUE.}
 
diff --git a/man/plot_locations.Rd b/man/plot_locations.Rd
index 15b9c71..b2aef19 100644
--- a/man/plot_locations.Rd
+++ b/man/plot_locations.Rd
@@ -8,7 +8,7 @@ plot_locations(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   mapzoom = 5,
   return_data = FALSE,
   jitter_value = 0.01,
@@ -22,9 +22,9 @@ plot_locations(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{mapzoom}{Value for zoom into the map passed down to \code{\link[ggmap]{get_map}}. Default value is 5. Higher zoom will auto-download more map files which can take a while.}
 
diff --git a/man/plot_media.Rd b/man/plot_media.Rd
index 6f56d27..45ed271 100644
--- a/man/plot_media.Rd
+++ b/man/plot_media.Rd
@@ -8,7 +8,7 @@ plot_media(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   use_filetype = TRUE,
   min_occur = 1,
   return_data = FALSE,
@@ -22,9 +22,9 @@ plot_media(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{use_filetype}{If TRUE, shortens sent file attachments to file types.}
 
diff --git a/man/plot_messages.Rd b/man/plot_messages.Rd
index 1e1ab42..e9e6bbc 100644
--- a/man/plot_messages.Rd
+++ b/man/plot_messages.Rd
@@ -8,7 +8,7 @@ plot_messages(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   plot = "bar",
   return_data = FALSE,
   exclude_sm = FALSE
@@ -19,9 +19,9 @@ plot_messages(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{plot}{Type of plot to be returned, options are "bar", "cumsum", "heatmap" and "pie". Default is "bar".}
 
diff --git a/man/plot_network.Rd b/man/plot_network.Rd
index a63b35b..2071485 100644
--- a/man/plot_network.Rd
+++ b/man/plot_network.Rd
@@ -8,7 +8,7 @@ plot_network(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   return_data = FALSE,
   collapse_sessions = FALSE,
   edgetype = "n",
@@ -20,9 +20,9 @@ plot_network(
 
 \item{names}{A vector of author names that the visualization will be restricted to. Non-listed authors will be removed.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Input is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Input is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{return_data}{If TRUE, returns a data frame of subsequent interactions with senders and recipients. Default is FALSE.}
 
diff --git a/man/plot_replytimes.Rd b/man/plot_replytimes.Rd
index 480acf7..9950bb6 100644
--- a/man/plot_replytimes.Rd
+++ b/man/plot_replytimes.Rd
@@ -8,7 +8,7 @@ plot_replytimes(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   return_data = FALSE,
   aggregate_sessions = TRUE,
   plot = "box",
@@ -21,9 +21,9 @@ plot_replytimes(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{return_data}{If TRUE, returns a data frame of response times extracted from the chat for more elaborate plotting. Default is FALSE.}
 
diff --git a/man/plot_smilies.Rd b/man/plot_smilies.Rd
index 22ea9fe..502b906 100644
--- a/man/plot_smilies.Rd
+++ b/man/plot_smilies.Rd
@@ -8,7 +8,7 @@ plot_smilies(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   min_occur = 1,
   return_data = FALSE,
   smilie_vec = "all",
@@ -21,9 +21,9 @@ plot_smilies(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{min_occur}{The minimum number of occurrences a smiley has to have to be included in the visualization. Default is 1.}
 
diff --git a/man/plot_tokens.Rd b/man/plot_tokens.Rd
index 301bf8e..a0f3755 100644
--- a/man/plot_tokens.Rd
+++ b/man/plot_tokens.Rd
@@ -8,7 +8,7 @@ plot_tokens(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   plot = "bar",
   return_data = FALSE,
   exclude_sm = FALSE
@@ -19,9 +19,9 @@ plot_tokens(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{plot}{The type of plot to be used. Options include "bar","box","violin" and "cumsum". Default is "bar".}
 
diff --git a/man/plot_tokens_over_time.Rd b/man/plot_tokens_over_time.Rd
index dec3db0..a5dba13 100644
--- a/man/plot_tokens_over_time.Rd
+++ b/man/plot_tokens_over_time.Rd
@@ -9,7 +9,7 @@ plot_tokens_over_time(
   names = "all",
   names_col = "Sender",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   plot = "alltime",
   return_data = FALSE,
   exclude_sm = FALSE
@@ -22,9 +22,9 @@ plot_tokens_over_time(
 
 \item{names_col}{A column indicated by a string that should be accessed to determine the names. Only needs to be changed when \code{\link[WhatsR]{parse_chat}} used the parameter anon = "add" and the column "Anonymous" should be used. Default is "Sender".}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{plot}{Type of plot to be returned. Options are "year", "day", "hour", "heatmap" and "alltime". Default is "alltime".}
 
diff --git a/man/plot_wordcloud.Rd b/man/plot_wordcloud.Rd
index e25ac16..71ad3ca 100644
--- a/man/plot_wordcloud.Rd
+++ b/man/plot_wordcloud.Rd
@@ -8,7 +8,7 @@ plot_wordcloud(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   remove_stops = TRUE,
   stop = "english",
   comparison = FALSE,
@@ -23,9 +23,9 @@ plot_wordcloud(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{remove_stops}{Either TRUE or FALSE, default is TRUE. Configures whether stopwords from \code{\link[tm]{stopwords}} are removed from the text strings.}
 
diff --git a/man/summarize_tokens_per_person.Rd b/man/summarize_tokens_per_person.Rd
index ce69aad..30b7876 100644
--- a/man/summarize_tokens_per_person.Rd
+++ b/man/summarize_tokens_per_person.Rd
@@ -8,7 +8,7 @@ summarize_tokens_per_person(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   exclude_sm = FALSE
 )
 }
@@ -17,9 +17,9 @@ summarize_tokens_per_person(
 
 \item{names}{A vector of author names that the plots will be restricted to.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{exclude_sm}{If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.}
 }
diff --git a/man/tailor_chat.Rd b/man/tailor_chat.Rd
index f65a812..db32529 100644
--- a/man/tailor_chat.Rd
+++ b/man/tailor_chat.Rd
@@ -8,7 +8,7 @@ tailor_chat(
   data,
   names = "all",
   starttime = "1960-01-01 00:00",
-  endtime = as.character(Sys.time()),
+  endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   exclude_sm = FALSE
 )
 }
@@ -17,9 +17,9 @@ tailor_chat(
 
 \item{names}{A vector of names that the output is restricted to. Messages from other non-contained authors are excluded.}
 
-\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{starttime}{Datetime that is used as the minimum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
-\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm".}
+\item{endtime}{Datetime that is used as the maximum boundary for exclusion. Is parsed with \code{\link[anytime]{anytime}}. Standard format is "yyyy-mm-dd hh:mm". Is interpreted as UTC to be compatible with WhatsApp timestamps.}
 
 \item{exclude_sm}{If TRUE, excludes the WhatsApp system messages from the descriptive statistics. Default is FALSE.}
 }
diff --git a/tests/testthat/Rplots.pdf b/tests/testthat/Rplots.pdf
new file mode 100644
index 0000000..e5eed98
Binary files /dev/null and b/tests/testthat/Rplots.pdf differ
diff --git a/tests/testthat/test-WhatsR-tests.R b/tests/testthat/test-WhatsR-tests.R
index 74d30e4..9470ae0 100644
--- a/tests/testthat/test-WhatsR-tests.R
+++ b/tests/testthat/test-WhatsR-tests.R
@@ -1,5 +1,6 @@
 #################### TESTING ESSENTIAL FUNCTIONS #####################
 
+
 #### Testing updating of emoji dictionary
 
 test_that("Updating emoji dictionary",{
@@ -908,20 +909,20 @@ test_that("tailoring function", {
   tailored_data3 <- tailor_chat(data,
     names = "Dave",
     starttime = "2018-01-29 12:24:03",
-    endtime = "2018-01-30 00:13:03",
+    endtime = "2018-01-29 23:33:03",
     exclude_sm = TRUE
   )
 
   # generate and write file [Use this to recreate test files when parse_chat() changed]
   #saveRDS(tailored_data3,"TailoredData3.rds",version = 2)
 
-  tailored_data <- readRDS(system.file("TailoredData3.rds", package = "WhatsR"))
+  test <- readRDS(system.file("TailoredData3.rds", package = "WhatsR"))
   expect_identical(test, tailored_data3)
 
   tailored_data4 <- tailor_chat(data,
     names = "all",
     starttime = "2018-01-29 12:24:03",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     exclude_sm = TRUE
   )
 
@@ -969,7 +970,6 @@ suppressWarnings(test_that("Plotting Emoji", {
   test <- readRDS(system.file("test_emoji1.rds", package = "WhatsR"))
   suppressWarnings(expect_identical(test_emoji1, test))
 
-
   test_emoji2 <- hush(plot_emoji(data,
     names = "all",
     # starttime=,
@@ -989,7 +989,6 @@ suppressWarnings(test_that("Plotting Emoji", {
   test <- readRDS(system.file("test_emoji2.rds", package = "WhatsR"))
   expect_identical(test_emoji2, test)
 
-
   test_emoji3 <- hush(plot_emoji(data,
     names = "all",
     # starttime=,
@@ -1044,7 +1043,7 @@ test_that("Plotting Links", {
   test_links1 <- plot_links(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_domains = TRUE,
     exclude_long = 50,
     min_occur = 1,
@@ -1061,11 +1060,10 @@ test_that("Plotting Links", {
   expect_identical(test_links1, test)
 
 
-
   test_links2 <- plot_links(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_domains = TRUE,
     exclude_long = 50,
     min_occur = 1,
@@ -1081,13 +1079,10 @@ test_that("Plotting Links", {
   test <- readRDS(system.file("test_links2.rds", package = "WhatsR"))
   expect_identical(test_links2, test)
 
-
-
-
   test_links3 <- plot_links(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_domains = FALSE,
     exclude_long = 50,
     min_occur = 1,
@@ -1108,7 +1103,7 @@ test_that("Plotting Links", {
   test_links4 <- plot_links(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_domains = TRUE,
     exclude_long = 50,
     min_occur = 1,
@@ -1137,11 +1132,10 @@ test_that("Plotting Media", {
 
   data <- hush(parse_chat(system.file("englishiosampm.txt", package = "WhatsR")))
 
-
   test_media1 <- plot_media(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_filetype = TRUE,
     min_occur = 1,
     return_data = TRUE,
@@ -1159,7 +1153,7 @@ test_that("Plotting Media", {
   test_media2 <- plot_media(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_filetype = FALSE,
     min_occur = 1,
     return_data = TRUE,
@@ -1174,14 +1168,10 @@ test_that("Plotting Media", {
   test <- readRDS(system.file("test_media2.rds", package = "WhatsR"))
   expect_identical(test_media2, test)
 
-
-  # TODO: `geom_line()`: Each group consists of only one observation.
-  # ℹ Do you need to adjust the group aesthetic?
-  # invalid font type for hjust bullshit
   test_media3 <- plot_media(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_filetype = TRUE,
     min_occur = 1,
     return_data = TRUE,
@@ -1199,7 +1189,7 @@ test_that("Plotting Media", {
   test_media4 <- plot_media(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     use_filetype = TRUE,
     min_occur = 1,
     return_data = TRUE,
@@ -1307,7 +1297,7 @@ test_that("Plotting Messages", {
   test_messages1 <- plot_messages(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "bar",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1319,14 +1309,10 @@ test_that("Plotting Messages", {
   test <- readRDS(system.file("test_messages1.rds", package = "WhatsR"))
   expect_identical(test_messages1, test)
 
-
-
-
-
   test_messages2 <- plot_messages(data,
     names = c("Carol", "Dave"),
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "bar",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1338,12 +1324,10 @@ test_that("Plotting Messages", {
   test <- readRDS(system.file("test_messages2.rds", package = "WhatsR"))
   expect_identical(test_messages2, test)
 
-
-
   test_messages3 <- plot_messages(data,
     names = "all",
     starttime = "2018-01-30 00:11:20",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "pie",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1355,13 +1339,10 @@ test_that("Plotting Messages", {
   test <- readRDS(system.file("test_messages3.rds", package = "WhatsR"))
   expect_identical(test_messages3, test)
 
-
-
-
   test_messages4 <- plot_messages(data,
     names = c("Alice", "Bob"),
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "pie",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1389,7 +1370,7 @@ test_that("Plotting Replytimes", {
   test_replytimes1 <- suppressMessages(plot_replytimes(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     aggregate_sessions = TRUE,
     plot = "box",
@@ -1407,7 +1388,7 @@ test_that("Plotting Replytimes", {
   test_replytimes2 <- suppressMessages(plot_replytimes(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     aggregate_sessions = TRUE,
     plot = "box",
@@ -1425,7 +1406,7 @@ test_that("Plotting Replytimes", {
   test_replytimes3 <- plot_replytimes(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     aggregate_sessions = TRUE,
     plot = "heatmap",
@@ -1443,7 +1424,7 @@ test_that("Plotting Replytimes", {
   test_replytimes4 <- plot_replytimes(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     aggregate_sessions = TRUE,
     plot = "heatmap",
@@ -1474,7 +1455,7 @@ test_that("Plotting tokens", {
   test_tokens1 <- suppressMessages(plot_tokens(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "bar",
     exclude_sm = TRUE,
     return_data = TRUE
@@ -1489,7 +1470,7 @@ test_that("Plotting tokens", {
   test_tokens2 <- suppressMessages(plot_tokens(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "cumsum",
     exclude_sm = TRUE,
     return_data = TRUE
@@ -1505,7 +1486,7 @@ test_that("Plotting tokens", {
   test_tokens3 <- suppressMessages(plot_tokens(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "violin",
     exclude_sm = TRUE,
     return_data = TRUE
@@ -1521,7 +1502,7 @@ test_that("Plotting tokens", {
   test_tokens4 <- suppressMessages(plot_tokens(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "box",
     exclude_sm = TRUE,
     return_data = TRUE
@@ -1549,7 +1530,7 @@ test_that("Plotting tokens over time", {
   test_tot1 <- suppressMessages(plot_tokens_over_time(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "alltime",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1565,7 +1546,7 @@ test_that("Plotting tokens over time", {
   test_tot2 <- suppressMessages(plot_tokens_over_time(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "year",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1581,7 +1562,7 @@ test_that("Plotting tokens over time", {
   test_tot3 <- suppressMessages(plot_tokens_over_time(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "day",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1597,7 +1578,7 @@ test_that("Plotting tokens over time", {
   test_tot4 <- suppressMessages(plot_tokens_over_time(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     plot = "heatmap",
     return_data = TRUE,
     exclude_sm = TRUE
@@ -1621,11 +1602,10 @@ test_that("Plotting Smilies", {
 
   data <- hush(parse_chat(system.file("englishiosampm.txt", package = "WhatsR")))
 
-
   test_smilies1 <- plot_smilies(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     min_occur = 1,
     return_data = TRUE,
     smilie_vec = "all",
@@ -1643,7 +1623,7 @@ test_that("Plotting Smilies", {
   test_smilies2 <- plot_smilies(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     min_occur = 1,
     return_data = TRUE,
     smilie_vec = "all",
@@ -1657,11 +1637,12 @@ test_that("Plotting Smilies", {
   test <- readRDS(system.file("test_smilies2.rds", package = "WhatsR"))
   expect_identical(test_smilies2, test)
 
-  #TODO: ERROR: invalid font type [only occurs in testing, not in use]
+  # TODO: This fails only when running check from RStudio, not with devtools::test()
+  # Seems to be a bug: https://github.com/hadley/r-pkgs/issues/483
   # test_smilies3 <- plot_smilies(data,
   #   names = "all",
-  #   starttime = anytime("1960-01-01 00:00",asUTC = TRUE),
-  #   endtime = Sys.time(),
+  #   starttime = "1960-01-01 00:00",
+  #   endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   #   min_occur = 1,
   #   return_data = TRUE,
   #   smilie_vec = "all",
@@ -1671,13 +1652,13 @@ test_that("Plotting Smilies", {
   # generate and write file [Use this to recreate test files when parse_chat() changed]
   #saveRDS(test_smilies3,"test_smilies3.rds",version = 2)
 
-  #test <- readRDS(system.file("test_smilies3.rds", package = "WhatsR"))
-  #expect_identical(test_smilies3,test)
+  # test <- readRDS(system.file("test_smilies3.rds", package = "WhatsR"))
+  # expect_identical(test_smilies3,test)
 
   test_smilies4 <- plot_smilies(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     min_occur = 1,
     return_data = TRUE,
     smilie_vec = "all",
@@ -1707,7 +1688,7 @@ test_that("Plotting Wordcloud", {
   test_wc1 <- plot_wordcloud(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     remove_stops = TRUE,
     stop = "english",
     comparison = FALSE,
@@ -1728,7 +1709,7 @@ test_that("Plotting Wordcloud", {
   test_wc2 <- plot_wordcloud(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     remove_stops = FALSE,
     stop = "english",
     comparison = TRUE,
@@ -1747,7 +1728,7 @@ test_that("Plotting Wordcloud", {
   test_wc3 <- plot_wordcloud(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     remove_stops = TRUE,
     stop = "english",
     comparison = FALSE,
@@ -1767,7 +1748,7 @@ test_that("Plotting Wordcloud", {
   test_wc4 <- plot_wordcloud(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     remove_stops = FALSE,
     stop = "english",
     comparison = TRUE,
@@ -1798,7 +1779,7 @@ test_that("Plotting Network", {
   test_network1 <- plot_network(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     collapse_sessions = FALSE,
     edgetype = "n",
@@ -1811,12 +1792,12 @@ test_that("Plotting Network", {
   test <- readRDS(system.file("test_network1.rds", package = "WhatsR"))
   expect_identical(test_network1, test)
 
-
-  # TODO: Error in `data.frame(..., check.names = FALSE)`: arguments imply differing number of rows: 1, 34 [only occurs in testing, not in use]
+  # TODO: This fails only when running check from RStudio, not with devtools::test()
+  # Seems to be a bug: https://github.com/hadley/r-pkgs/issues/483
   # test_network2 <- plot_network(data,
   #   names = "all",
-  #   starttime = anytime("1960-01-01 00:00",asUTC = TRUE),
-  #   endtime = Sys.time(),
+  #   starttime = "1960-01-01 00:00",
+  #   endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   #   return_data = TRUE,
   #   collapse_sessions = TRUE,
   #   edgetype = "TokCount",
@@ -1826,8 +1807,8 @@ test_that("Plotting Network", {
   # generate and write file [Use this to recreate test files when parse_chat() changed]
   #saveRDS(test_network2,"test_network2.rds",version = 2)
 
-  #test <- readRDS(system.file("test_network2.rds", package = "WhatsR"))
-  #expect_identical(test_network2, test)
+  # test <- readRDS(system.file("test_network2.rds", package = "WhatsR"))
+  # expect_identical(test_network2, test)
 
   test_network3 <- plot_network(data,
     names = "all",
@@ -1845,20 +1826,21 @@ test_that("Plotting Network", {
   test <- readRDS(system.file("test_network3.rds", package = "WhatsR"))
   expect_identical(test_network3, test)
 
-  # TODO: Error in `data.frame(..., check.names = FALSE)`: arguments imply differing number of rows: 1, 34 [only occurs in testing, not in use]
+  # TODO: This fails only when running check from RStudio, not with devtools::test()
+  # Seems to be a bug: https://github.com/hadley/r-pkgs/issues/483
   # test_network4 <- plot_network(data,
   #   names = "all",
-  #   starttime = anytime("1960-01-01 00:00",asUTC = TRUE),
-  #   endtime = Sys.time(),
+  #   starttime = "1960-01-01 00:00",
+  #   endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
   #   return_data = TRUE,
   #   collapse_sessions = TRUE,
   #   edgetype = "SmilieCount",
   #   exclude_sm = TRUE
   # )
-  #
+
   # # generate and write file [Use this to recreate test files when parse_chat() changed]
   # #saveRDS(test_network4,"test_network4.rds",version = 2)
-  #
+
   # test <- readRDS(system.file("test_network4.rds", package = "WhatsR"))
   # expect_identical(test_network4, test)
 })
@@ -1877,7 +1859,7 @@ test_that("Plotting Lexical Dispersion", {
   test_lediplo1 <- plot_lexical_dispersion(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     keywords = c("data", "consent"),
     exclude_sm = TRUE
@@ -1892,7 +1874,7 @@ test_that("Plotting Lexical Dispersion", {
   test_lediplo2 <- plot_lexical_dispersion(data,
     names = c("Alice", "Bob"),
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     keywords = c("data", "consent"),
     exclude_sm = TRUE
@@ -1908,7 +1890,7 @@ test_that("Plotting Lexical Dispersion", {
   test_lediplo3 <- plot_lexical_dispersion(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     keywords = c("data", "consent", "this"),
     exclude_sm = TRUE
@@ -1924,7 +1906,7 @@ test_that("Plotting Lexical Dispersion", {
   test_lediplo4 <- plot_lexical_dispersion(data,
     names = "all",
     starttime = "1960-01-01 00:00",
-    endtime = as.character(Sys.time()),
+    endtime = as.character(as.POSIXct(Sys.time(), tz = "UTC")),
     return_data = TRUE,
     keywords = c("data", "consent"),
     exclude_sm = TRUE