Fix bug in free busy report serializing a datetime tzinfo

radicale/app/report.py

@@ -65,6 +65,7 @@ def free_busy_report(base_prefix: str, path: str, xml_request: Optional[ET.Eleme
             vfb.add('dtstart').value, vfb.add('dtend').value = occurrence
     return (client.OK, cal.serialize())
 
+
 def xml_report(base_prefix: str, path: str, xml_request: Optional[ET.Element],
                collection: storage.BaseCollection, encoding: str,
                unlock_storage_fn: Callable[[], None]

radicale/item/filter.py

@@ -48,7 +48,8 @@ def date_to_datetime(d: date) -> datetime:
     if not isinstance(d, datetime):
         d = datetime.combine(d, datetime.min.time())
     if not d.tzinfo:
-        d = d.replace(tzinfo=timezone.utc)
+        # NOTE: using vobject's UTC as it wasn't playing well with datetime's.
+        d = d.replace(tzinfo=vobject.icalendar.utc)
     return d