Convert RRULE UNTIL with no tzinfo to UTC

Since DTSTART is always given tzinfo, any UNTIL in an RRULE
must be tz-aware and in UTC.

See: irgangla/icalevents#47

icalevents/icalparser.py

@@ -259,6 +259,15 @@ def parse_rrule(component, tz=UTC):
         rrules = component['rrule']
         if not isinstance(rrules, list):
             rrules = [rrules]
+
+        # Since DTSTART are always made timezone aware, UNTIL with no tzinfo
+        # must be converted to UTC.
+        for rule in rrules:
+            until = rule.get("until")
+            for idx, dt in enumerate(until or []):
+                if not hasattr(dt, 'tzinfo'):
+                    until[idx] = normalize(normalize(dt, tz=tz), tz=UTC)
+
         # Parse the rrules, might return a rruleset instance, instead of rrule
         rule = rrulestr('\n'.join(x.to_ical().decode() for x in rrules), dtstart=normalize(component['dtstart'].dt, tz=tz))
         

test/test_data/rrule_until.ics

@@ -0,0 +1,19 @@
+BEGIN:VCALENDAR
+BEGIN:VTIMEZONE
+TZID:Europe/Berlin
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTART;VALUE=DATE:20151030
+DTEND;VALUE=DATE:20151031
+DESCRIPTION:All-day event recurring on tuesday each week
+SUMMARY:Recurring All-day Event
+RRULE:FREQ=WEEKLY;BYDAY=TU;UNTIL=20341031
+END:VEVENT
+BEGIN:VEVENT
+DTSTART;TZID=Europe/London:20180522T120000
+DTEND;TZID=Europe/London:20180522T130000
+DESCRIPTION:Daily lunchtime event with specified hours
+SUMMARY:Daily lunch event
+RRULE:FREQ=DAILY;UNTIL=20330523T060000Z
+END:VEVENT
+END:VCALENDAR

test/test_icalevents.py

@@ -107,6 +107,18 @@ class ICalEventsTests(unittest.TestCase):
         self.assertEqual(ev_2.description, "All-day event recurring on tuesday each week")
         self.assertTrue(ev_2.all_day, "Recurring All-day Event's second instance is an all-day event")
 
+    def test_events_rrule_until(self):
+        ical = "test/test_data/rrule_until.ics"
+        start = date(2019, 4, 2)
+        end = date(2019, 4, 3)
+
+        evs = icalevents.events(file=ical, start=start, end=end)
+
+        self.assertEqual(len(evs), 2)
+        self.assertEqual(evs[0].recurring, True)
+        self.assertEqual(evs[0].summary, "Recurring All-day Event")
+        self.assertEqual(evs[1].recurring, True)
+        self.assertEqual(evs[1].summary, "Daily lunch event")
 
     def test_event_attributes(self):
         ical = "test/test_data/basic.ics"