fix(web): Inconsistent exclusive/inclusive end dates for allday events

Author: that-one-arab

packages/web/src/common/utils/web.date.util.ts

@@ -221,9 +221,19 @@ export const getCalendarHeadingLabel = (
 
 export const mapToBackend = (s: Schema_SelectedDates) => {
   if (s.isAllDay) {
+    const startDate = dayjs(s.startDate).format(YEAR_MONTH_DAY_FORMAT);
+    const endDate = dayjs(s.endDate).format(YEAR_MONTH_DAY_FORMAT);
+
+    if (startDate === endDate) {
+      return {
+        startDate,
+        endDate: dayjs(endDate).add(1, "day").format(YEAR_MONTH_DAY_FORMAT),
+      };
+    }
+
     return {
-      startDate: dayjs(s.startDate).format(YEAR_MONTH_DAY_FORMAT),
-      endDate: dayjs(s.endDate).format(YEAR_MONTH_DAY_FORMAT),
+      startDate,
+      endDate,
     };
   }
 

packages/web/src/ducks/events/sagas/saga.util.ts

@@ -98,14 +98,18 @@ export const EventDateUtils = {
   ) => {
     return events.filter((event) => {
       if (event.isAllDay) {
-        const belongsInRange =
-          dayjs(event.startDate).isSameOrAfter(startDate) ||
-          dayjs(event.endDate).isSameOrBefore(endDate) ||
-          // is between start and end date
-          (dayjs(startDate).isBetween(event.startDate, event.endDate) &&
-            dayjs(endDate).isBetween(event.startDate, event.endDate));
+        // For all-day events with exclusive end dates (e.g., Mon event: start="2025-09-08", end="2025-09-09")
+        // Check if the event overlaps with the requested date range
+        const eventStart = dayjs(event.startDate);
+        const eventEnd = dayjs(event.endDate); // This is exclusive, so actual event ends the day before
+        const rangeStart = dayjs(startDate);
+        const rangeEnd = dayjs(endDate);
 
-        return belongsInRange;
+        // Event overlaps if: event starts before range ends AND event ends after range starts
+        const overlaps =
+          eventStart.isBefore(rangeEnd) && eventEnd.isAfter(rangeStart);
+
+        return overlaps;
       }
 
       return (