[#425] Event title modification of all day event alter event dates (#431)

Co-authored-by: Camille Moussu <cmoussu@linagora.com>

__test__/features/Events/eventUtils.test.ts

@@ -513,12 +513,12 @@ describe("calendarEventToJCal", () => {
     );
   });
 
-  it("converts all-day events adjusting dtend", () => {
+  it("converts all-day events", () => {
     const mockEvent: any = {
       uid: "event-11",
       title: "All Day",
       start: "2025-07-21T00:00:00.000Z",
-      end: "2025-07-21T00:00:00.000Z",
+      end: "2025-07-22T00:00:00.000Z",
       timezone: "Europe/Paris",
       allday: true,
       attendee: [],
@@ -542,7 +542,7 @@ describe("calendarEventToJCal", () => {
       calId: "test/test",
       title: "Team Meeting",
       start: "2025-07-23T00:00:00.000Z",
-      end: "2025-07-23T00:00:00.000Z",
+      end: "2025-07-24T00:00:00.000Z",
       timezone: "Europe/Paris",
       transp: "OPAQUE",
       class: "PUBLIC",

src/features/Events/EventDisplayPreview.tsx

@@ -994,18 +994,21 @@ function formatEnd(
 
   const formatDatePart = (d: Date) =>
     d.toLocaleDateString("en-CA", { timeZone }); // YYYY-MM-DD format
-  const sameDay = formatDatePart(startDate) === formatDatePart(endDate);
-
   if (allday) {
+    const inclusiveEndDate = new Date(endDate);
+    inclusiveEndDate.setDate(inclusiveEndDate.getDate() - 1);
+    const sameDay =
+      formatDatePart(startDate) === formatDatePart(inclusiveEndDate);
     return sameDay
       ? null
-      : endDate.toLocaleDateString(t("locale"), {
+      : inclusiveEndDate.toLocaleDateString(t("locale"), {
           year: "numeric",
           month: "short",
           day: "numeric",
           timeZone,
         });
   } else {
+    const sameDay = formatDatePart(startDate) === formatDatePart(endDate);
     if (sameDay) {
       return endDate.toLocaleTimeString(t("locale"), {
         hour: "2-digit",

src/features/Events/EventUpdateModal.tsx

@@ -247,6 +247,7 @@ function EventUpdateModal({
         if (isAllDay) {
           // For all-day events, use date format (YYYY-MM-DD)
           const endDate = new Date(event.end);
+          endDate.setDate(endDate.getDate() - 1);
           setEnd(endDate.toISOString().split("T")[0]);
         } else {
           // For timed events, format in the event's original timezone

src/features/Events/eventUtils.ts

@@ -331,11 +331,6 @@ export function makeVevent(
     const endDate = new Date(event.end);
     let finalEndDate = endDate;
 
-    if (event.allday && endDate.getTime() === startDate.getTime()) {
-      finalEndDate = new Date(endDate);
-      finalEndDate.setDate(startDate.getDate() + 1);
-    }
-
     vevent[1].push([
       "dtend",
       { tzid },