Default to UTC timezone

pyproject.toml

@@ -89,6 +89,7 @@ ignore = [
   "ARG001",   # Unused function argument
   "PT012",    # `pytest.raises()` block
   "PLW0129",  # Asserting on a non-empty string literal will always pass
+  "SIM108",   # Use ternary operator instead of `if`-`else`-block
 ]
 
 [tool.pytest.ini_options]

tests/test_events.py

@@ -173,3 +173,19 @@ def test_events_with_multiple_timezones():
     assert events[1].begin.tzname() in ("UTC", "Coordinated Universal Time")
     assert events[2].begin.tzname() == "PDT"
     assert events[3].begin.tzname() == "PST"
+
+
+def test_events_without_timezone():
+    f = io.BytesIO(b"""
+        name: Default Timezone
+        events:
+          - summary: Meeting A
+            begin: 2025-09-02 17:00:00
+            duration: { minutes: 60 }
+          - summary: Meeting B
+            begin: 2025-12-01 09:00:00
+            end: 2025-12-01 10:00:00
+    """)
+    events, _ = files_to_events([f])
+    assert events[0].begin.tzname() in ("UTC", "Coordinated Universal Time")
+    assert events[1].begin.tzname() in ("UTC", "Coordinated Universal Time")

yaml2ics.py

@@ -52,18 +52,20 @@ def gettz(tzname: str) -> datetime.tzinfo:
 # This function can be used to add a list of e.g. exception dates (EXDATE) or
 # recurrence dates (RDATE) to a reoccurring event
 def add_recurrence_property(
-    event: ics.Event, property_name, dates: map, tz: datetime.tzinfo = None
+    event: ics.Event, property_name, dates: map, tz: datetime.tzinfo = dateutil.tz.UTC
 ):
     event.extra.append(
         ics.ContentLine(
             name=property_name,
-            params={"TZID": [str(ics.Timezone.from_tzinfo(tz))]} if tz else None,
+            params={"TZID": [str(ics.Timezone.from_tzinfo(tz))]},
             value=",".join(dates),
         )
     )
 
 
-def event_from_yaml(event_yaml: dict, tz: datetime.tzinfo = None) -> ics.Event:
+def event_from_yaml(
+    event_yaml: dict, tz: datetime.tzinfo = dateutil.tz.UTC
+) -> ics.Event:
     d = event_yaml
     repeat = d.pop("repeat", None)
     ics_custom = d.pop("ics", None)
@@ -184,6 +186,8 @@ def files_to_events(files: list) -> (ics.Calendar, str):
         tz = calendar_yaml.get("timezone", None)
         if tz is not None:
             tz = gettz(tz)
+        else:
+            tz = dateutil.tz.UTC
         if "include" in calendar_yaml:
             included_events, _name = files_to_events(
                 os.path.join(os.path.dirname(f), newfile)