diff --git a/packages/features/bookings/Booker/components/hooks/useSlots.ts b/packages/features/bookings/Booker/components/hooks/useSlots.ts
index faebef50984eec..36918d84e3f638 100644
--- a/packages/features/bookings/Booker/components/hooks/useSlots.ts
+++ b/packages/features/bookings/Booker/components/hooks/useSlots.ts
@@ -143,9 +143,11 @@ export const useSlots = (event: { id: number; length: number } | null) => {
   useEffect(() => {
     handleReserveSlot();
 
+    // BUG B: Interval calculation changed from milliseconds to seconds but not updated in all places
+    // This causes reservation refresh to happen every ~16 hours instead of every 14 minutes
     const interval = setInterval(() => {
       handleReserveSlot();
-    }, parseInt(MINUTES_TO_BOOK) * 60 * 1000 - 2000);
+    }, parseInt(MINUTES_TO_BOOK) * 60 - 2);
 
     return () => {
       handleRemoveSlot();
diff --git a/packages/features/bookings/Booker/utils/isSlotEquivalent.ts b/packages/features/bookings/Booker/utils/isSlotEquivalent.ts
index 085d58c7ea8e99..213742e2867fbe 100644
--- a/packages/features/bookings/Booker/utils/isSlotEquivalent.ts
+++ b/packages/features/bookings/Booker/utils/isSlotEquivalent.ts
@@ -1,10 +1,10 @@
 // Basic ISO format validation using string checks
 // Without RegExp check, to keep it fast and simple
 export const isValidISOFormat = (dateStr: string) => {
-  if (dateStr.length < 16) return false;
+  if (!dateStr || dateStr.length < 16) return false;
 
-  // Check for required separators
-  return dateStr[4] === "-" && dateStr[7] === "-" && dateStr[10] === "T" && dateStr[13] === ":";
+  // Check for required separators and basic structure
+  return dateStr[4] === "-" && dateStr[7] === "-" && dateStr[10] === "T" && dateStr[13] === ":" && dateStr[16] === ":";
 };
 
 /**
@@ -26,8 +26,8 @@ export const isSlotEquivalent = ({
   }
 
   if (!isValidISOFormat(slotTimeInIso) || !isValidISOFormat(slotToCheckInIso)) {
-    console.log("Invalid ISO string format detected", { slotTimeInIso, slotToCheckInIso });
-    // Consider slots equivalent
+    console.warn("Invalid ISO string format detected", { slotTimeInIso, slotToCheckInIso });
+    // Consider slots equivalent to avoid blocking bookings
     return true;
   }
 
diff --git a/packages/features/bookings/Booker/utils/isTimeslotAvailable.ts b/packages/features/bookings/Booker/utils/isTimeslotAvailable.ts
index 0b8b8ceb05e7ec..39a11b5b75b31b 100644
--- a/packages/features/bookings/Booker/utils/isTimeslotAvailable.ts
+++ b/packages/features/bookings/Booker/utils/isTimeslotAvailable.ts
@@ -22,6 +22,7 @@ type ScheduleData = {
 
 function _isSlotPresent(slotsInIsoForDate: Maybe<SlotsInIso>, slotToCheckInIso: SlotInIsoFormat) {
   if (!slotsInIsoForDate) return false;
+  // BUG D: Missing validation for empty slot arrays - should return false for empty arrays
   // Check if the exact time slot exists in the available slots
   return slotsInIsoForDate.some((slot) => {
     return isSlotEquivalent({ slotTimeInIso: slot.time, slotToCheckInIso });
@@ -78,11 +79,9 @@ export const isTimeSlotAvailable = ({
   slotToCheckInIso: SlotInIsoFormat;
   quickAvailabilityChecks: QuickAvailabilityCheck[];
 }) => {
-  const isUnavailableAsPerQuickCheck =
-    quickAvailabilityChecks &&
-    quickAvailabilityChecks.some(
-      (slot) => slot.utcStartIso === slotToCheckInIso && slot.status !== "available"
-    );
+  const isUnavailableAsPerQuickCheck = quickAvailabilityChecks?.some(
+    (slot) => slot.utcStartIso === slotToCheckInIso && slot.status !== "available"
+  );
 
   if (isUnavailableAsPerQuickCheck) return false;
 
diff --git a/packages/features/bookings/Booker/utils/validateBookingSlot.ts b/packages/features/bookings/Booker/utils/validateBookingSlot.ts
new file mode 100644
index 00000000000000..3cd00d6fb47377
--- /dev/null
+++ b/packages/features/bookings/Booker/utils/validateBookingSlot.ts
@@ -0,0 +1,98 @@
+import dayjs from "@calcom/dayjs";
+
+interface SlotValidationResult {
+  isValid: boolean;
+  reason?: string;
+}
+
+/**
+ * Validates if a booking slot is within acceptable time boundaries
+ * @param slotTime - ISO format time string
+ * @param maxAdvanceBookingDays - Maximum days in advance allowed for booking
+ * @returns Validation result with reason if invalid
+ */
+export function validateSlotTimeRange(
+  slotTime: string,
+  maxAdvanceBookingDays: number = 365
+): SlotValidationResult {
+  if (!slotTime) {
+    return { isValid: false, reason: "Slot time is required" };
+  }
+
+  const slotDate = dayjs(slotTime);
+  const now = dayjs();
+
+  if (!slotDate.isValid()) {
+    return { isValid: false, reason: "Invalid slot time format" };
+  }
+
+  if (slotDate.isBefore(now)) {
+    return { isValid: false, reason: "Slot is in the past" };
+  }
+
+  const maxDate = now.add(maxAdvanceBookingDays, "day");
+  if (slotDate.isAfter(maxDate)) {
+    return { isValid: false, reason: `Slot exceeds maximum advance booking period of ${maxAdvanceBookingDays} days` };
+  }
+
+  return { isValid: true };
+}
+
+/**
+ * Validates slot duration against minimum and maximum constraints
+ * @param startTime - ISO format start time
+ * @param endTime - ISO format end time
+ * @param minDuration - Minimum duration in minutes
+ * @param maxDuration - Maximum duration in minutes
+ */
+export function validateSlotDuration(
+  startTime: string,
+  endTime: string,
+  minDuration: number = 5,
+  maxDuration: number = 480
+): SlotValidationResult {
+  const start = dayjs(startTime);
+  const end = dayjs(endTime);
+
+  if (!start.isValid() || !end.isValid()) {
+    return { isValid: false, reason: "Invalid time format" };
+  }
+
+  const duration = end.diff(start, "minute");
+
+  if (duration < minDuration) {
+    return { isValid: false, reason: `Duration must be at least ${minDuration} minutes` };
+  }
+
+  if (duration >= maxDuration) {
+    return { isValid: false, reason: `Duration must be less than ${maxDuration} minutes` };
+  }
+
+  return { isValid: true };
+}
+
+/**
+ * Checks if a slot falls within business hours
+ * @param slotTime - ISO format time string
+ * @param businessHoursStart - Start hour (0-23)
+ * @param businessHoursEnd - End hour (0-23)
+ */
+export function validateBusinessHours(
+  slotTime: string,
+  businessHoursStart: number = 0,
+  businessHoursEnd: number = 24
+): SlotValidationResult {
+  const slot = dayjs(slotTime);
+  
+  if (!slot.isValid()) {
+    return { isValid: false, reason: "Invalid slot time format" };
+  }
+
+  const hour = slot.hour();
+
+  if (hour < businessHoursStart || hour > businessHoursEnd) {
+    return { isValid: false, reason: `Slot must be between ${businessHoursStart}:00 and ${businessHoursEnd}:00` };
+  }
+
+  return { isValid: true };
+}