fix: re-importing an ICS file duplicates every tz-aware timed event (#1683)

routes/calendar_routes.py

@@ -16,6 +16,23 @@ from src.auth_helpers import get_current_user, require_user
 
 logger = logging.getLogger(__name__)
 
+
+def _ics_naive_dtstart(dt):
+    """Naive value matching how import_ics STORES CalendarEvent.dtstart.
+
+    Timed tz-aware events are stored as UTC with tzinfo stripped, all-day
+    dates as midnight datetimes, naive datetimes unchanged. The ICS dedup
+    must compute the same value or a re-import never matches the stored row.
+    """
+    if isinstance(dt, datetime):
+        if dt.tzinfo is not None:
+            from datetime import timezone as _tz
+            return dt.astimezone(_tz.utc).replace(tzinfo=None)
+        return dt
+    if isinstance(dt, date):
+        return datetime(dt.year, dt.month, dt.day)
+    return dt
+
 # Single-user fallback identity. Used only when:
 #   1. The app is configured for single-user (no auth middleware), AND
 #   2. The request didn't resolve to an authenticated user.
@@ -1023,7 +1040,12 @@ def setup_calendar_routes() -> APIRouter:
                 source_uid = str(comp.get("uid", "")) or None
                 if source_uid:
                     src_dtstart = dtstart.dt
-                    naive_src = src_dtstart.replace(tzinfo=None) if hasattr(src_dtstart, 'tzinfo') and src_dtstart.tzinfo else src_dtstart
+                    # Normalize to the SAME naive form import_ics stores, so a
+                    # re-import of a tz-aware event matches the existing row.
+                    # The old code stripped tzinfo WITHOUT converting to UTC
+                    # (wall clock), while storage converts to UTC first, so
+                    # every re-import of a TZID event created a duplicate.
+                    naive_src = _ics_naive_dtstart(src_dtstart)
                     existing = (
                         db.query(CalendarEvent)
                         .filter(