diff --git a/adcircpy/forcing/base.py b/adcircpy/forcing/base.py
index 5fbf0573..ccc97134 100644
--- a/adcircpy/forcing/base.py
+++ b/adcircpy/forcing/base.py
@@ -1,8 +1,22 @@
 from abc import ABC, abstractmethod
+from datetime import timedelta
 from os import PathLike
 
 
 class Forcing(ABC):
+    def __init__(self, interval: timedelta):
+        self.interval = interval
+
     @abstractmethod
     def write(self, directory: PathLike, overwrite: bool = False):
         raise NotImplementedError
+
+    @property
+    def interval(self) -> timedelta:
+        return self.__interval
+
+    @interval.setter
+    def interval(self, interval: timedelta):
+        if not isinstance(interval, timedelta):
+            interval = timedelta(seconds=interval)
+        self.__interval = interval
diff --git a/adcircpy/forcing/waves/base.py b/adcircpy/forcing/waves/base.py
index 57fcff46..d0b44f58 100644
--- a/adcircpy/forcing/waves/base.py
+++ b/adcircpy/forcing/waves/base.py
@@ -6,8 +6,8 @@
 
 class WaveForcing(Forcing, ABC):
     def __init__(self, nrs: int, interval_seconds: int):
+        super().__init__(interval_seconds)
         self.NRS = nrs
-        self.RSTIMINC = interval_seconds
 
     @abstractmethod
     def write(self, directory: PathLike, overwrite: bool = False):
diff --git a/adcircpy/forcing/winds/base.py b/adcircpy/forcing/winds/base.py
index a623e7f0..518a94e6 100644
--- a/adcircpy/forcing/winds/base.py
+++ b/adcircpy/forcing/winds/base.py
@@ -6,8 +6,8 @@
 
 class WindForcing(Forcing, ABC):
     def __init__(self, nws: int, interval_seconds: int):
+        super().__init__(interval_seconds)
         self.NWS = nws
-        self.WTIMINC = interval_seconds
 
     @abstractmethod
     def write(self, directory: PathLike, overwrite: bool = False):
diff --git a/adcircpy/fort15.py b/adcircpy/fort15.py
index 968db8ca..ccc9e20a 100644
--- a/adcircpy/fort15.py
+++ b/adcircpy/fort15.py
@@ -987,7 +987,7 @@ def REFTIM(self):
     @property
     def WTIMINC(self):
         if self.NWS not in [0, 1, 9, 11]:
-            return self.wind_forcing.WTIMINC
+            return int(self.wind_forcing.interval / timedelta(seconds=1))
         else:
             return 0
 
@@ -995,7 +995,7 @@ def WTIMINC(self):
     def RSTIMINC(self):
         if self.NRS in [1, 3, 4, 5]:
             if self.wave_forcing is not None:
-                return self.wave_forcing.RSTIMINC
+                return int(self.wave_forcing.interval / timedelta(seconds=1))
             else:
                 return self.WTIMINC
         else: