Fixing timezone issue with caldav.

2026-02-19 02:09:36 +01:00
parent 564cb0b16f
commit 317113a1b3
4 changed files with 199 additions and 11 deletions
@@ -624,8 +624,8 @@ public sealed class CalDavClient : ICalDavClient
            Location = sourceEvent.Location ?? string.Empty,
            Start = start,
            End = end,
-            StartTimeZone = sourceEvent.Start?.TzId ?? string.Empty,
-            EndTimeZone = sourceEvent.End?.TzId ?? string.Empty,
+            StartTimeZone = ResolveTimeZoneId(sourceEvent.Start, start),
+            EndTimeZone = ResolveTimeZoneId(sourceEvent.End, end),
            Recurrence = recurrence,
            OrganizerDisplayName = organizerDisplayName,
            OrganizerEmail = organizerEmail,
@@ -638,6 +638,21 @@ public sealed class CalDavClient : ICalDavClient
        };
    }

+    private static string ResolveTimeZoneId(IDateTime sourceDateTime, DateTimeOffset parsedDateTime)
+    {
+        var explicitTimeZoneId = sourceDateTime?.TzId;
+        if (!string.IsNullOrWhiteSpace(explicitTimeZoneId))
+            return explicitTimeZoneId;
+
+        // Explicit UTC values usually don't carry TZID in CalDAV payloads.
+        // Preserve UTC so downstream local-time conversion stays correct.
+        if (parsedDateTime != default && parsedDateTime.Offset == TimeSpan.Zero)
+            return TimeZoneInfo.Utc.Id;
+
+        // Floating times without TZID should remain floating.
+        return string.Empty;
+    }
+
    private static string BuildRecurrenceString(CalendarEvent sourceEvent)
    {
        var recurrenceLines = new List<string>();