fix(calendar): keep recurrence times anchored to source timezone

- map recurring event instants with moment-timezone so viewer DST offsets stay correct
- leave floating metadata available for full-day cases while returning structured payloads
- update calendar fetcher unit spec to assert against the new occurrence wrapper

Author: KristjanESPERANTO

modules/default/calendar/calendar.js

@@ -589,12 +589,13 @@ Module.register("calendar", {
 	 * @returns {moment.Moment} moment with a timezone
 	 */
 	timestampToMoment (timestamp, isFullDayEvent = false, floatingDate = null) {
-		const viewerOffsetMinutes = -new Date().getTimezoneOffset();
+		const viewerTimezone = moment.tz.guess();
 		if (isFullDayEvent && floatingDate) {
-			return moment(floatingDate, "YYYY-MM-DD").utcOffset(viewerOffsetMinutes, true).startOf("day");
+			return moment.tz(floatingDate, "YYYY-MM-DD", viewerTimezone).startOf("day");
 		}
-		const baseMoment = moment(timestamp, "x").utc();
-		return baseMoment.clone().utcOffset(viewerOffsetMinutes, isFullDayEvent);
+		const timestampMs = parseInt(timestamp, 10);
+		const baseMoment = moment.utc(timestampMs);
+		return baseMoment.clone().tz(viewerTimezone, isFullDayEvent);
 	},
 
 	/**

tests/unit/modules/default/calendar/calendar_fetcher_utils_spec.js

@@ -104,13 +104,13 @@ SUMMARY:Test
 TRANSP:OPAQUE
 END:VEVENT`);
 
-			const moments = CalendarFetcherUtils.getMomentsFromRecurringEvent(data["67e65a1d-b889-4451-8cab-5518cecb9c66"], moment(), moment().add(365, "days"));
+			const occurrences = CalendarFetcherUtils.getMomentsFromRecurringEvent(data["67e65a1d-b889-4451-8cab-5518cecb9c66"], moment(), moment().add(365, "days"));
 
-			const januaryFirst = moments.filter((m) => m.format("MM-DD") === "01-01");
-			const julyFirst = moments.filter((m) => m.format("MM-DD") === "07-01");
+			const januaryFirst = occurrences.filter((entry) => entry.occurrence.format("MM-DD") === "01-01");
+			const julyFirst = occurrences.filter((entry) => entry.occurrence.format("MM-DD") === "07-01");
 
-			expect(januaryFirst[0].toISOString(true)).toContain("09:00:00.000+01:00");
-			expect(julyFirst[0].toISOString(true)).toContain("09:00:00.000+02:00");
+			expect(januaryFirst[0].occurrence.toISOString(true)).toContain("09:00:00.000+01:00");
+			expect(julyFirst[0].occurrence.toISOString(true)).toContain("09:00:00.000+02:00");
 		});
 	});
 });