problems with daylight saving times

[Ro-C-Me]

Hi,

not quite sure if it's ok to post this here, but... I'll give it a try :)

I'm trying to parse an ICS file from office365 / outlook. It's seems to work in general, but I always get the results with "+02:00" (probably European summer time) instead of "+01:00" (European winter time).

Probably, this isn't a issue with the library, but with me or my code, but even after thinking for days, I can't figure out whats wrong...

Here is what I'm currently doing in my unit test:

	@Test
	public void testRecurringWednesday_minimal() throws FileNotFoundException, IOException, ParserException {
		File testFile = new File("src/test/resources/recurring_wednesday.ics");
		assertTrue(testFile.exists(), "test file not found: " + testFile.getAbsolutePath());
		
		Calendar calendar = null;
		TimeZoneRegistry createRegistry = new OutlookTimeZoneRegistryFactory().createRegistry();
		calendar = new CalendarBuilder(createRegistry)
				.build(new DataInputStream(new FileInputStream(testFile)));
		
		ZonedDateTime begin = ZonedDateTime.of(2022, 11, 30, 0, 0, 0, 0, ZoneId.of("Europe/Berlin"));
		Period period = new Period<Temporal>(begin, Minutes.of(1600));
		// TODO how to remove all CANCELLED events?
		Filter<VEvent> filter = new Filter<VEvent>(new PeriodRule(period ));

		Collection<VEvent> upcoming = filter
				.filter(calendar.getComponents(net.fortuna.ical4j.model.Component.VEVENT));

		log.info("Found " + upcoming.size() + " events");
		upcoming.stream().forEach(e -> {
			Set<Period<Temporal>> recs = e.calculateRecurrenceSet(period);
			recs.stream().forEach(r-> {log.info("Begin: " + r.getStart());});
		});

	}

My (test) ics calendar content with 2 events is:

BEGIN:VCALENDAR
METHOD:PUBLISH
PRODID:Microsoft Exchange Server 2010
VERSION:2.0
X-WR-CALNAME:Kalender
BEGIN:VTIMEZONE
TZID:W. Europe Standard Time
BEGIN:STANDARD
DTSTART:16010101T030000
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=-1SU;BYMONTH=10
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T020000
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=-1SU;BYMONTH=3
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VTIMEZONE
TZID:UTC
BEGIN:STANDARD
DTSTART:16010101T000000
TZOFFSETFROM:+0000
TZOFFSETTO:+0000
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:16010101T000000
TZOFFSETFROM:+0000
TZOFFSETTO:+0000
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
RRULE:FREQ=WEEKLY;UNTIL=20230517T073000Z;INTERVAL=1;BYDAY=WE;WKST=SU
UID:040000008200E00074C5B7101A82E00800000000C6C9CF59F6D9D701000000000000000
 010000000CAD7F28AF2E7284AB42C744A1579929E
SUMMARY:Gebucht
DTSTART;TZID=W. Europe Standard Time:20221026T093000
DTEND;TZID=W. Europe Standard Time:20221026T100000
CLASS:PUBLIC
PRIORITY:5
DTSTAMP:20221120T215710Z
TRANSP:OPAQUE
STATUS:CONFIRMED
SEQUENCE:2
X-MICROSOFT-CDO-APPT-SEQUENCE:2
X-MICROSOFT-CDO-BUSYSTATUS:BUSY
X-MICROSOFT-CDO-INTENDEDSTATUS:BUSY
X-MICROSOFT-CDO-ALLDAYEVENT:FALSE
X-MICROSOFT-CDO-IMPORTANCE:1
X-MICROSOFT-CDO-INSTTYPE:1
X-MICROSOFT-DONOTFORWARDMEETING:FALSE
X-MICROSOFT-DISALLOW-COUNTER:FALSE
END:VEVENT
BEGIN:VEVENT
UID:040000008200E00074C5B7101A82E0080000000039D3E9AD4100D901000000000000000
 0100000008A2284A522B45947B4A4B5059BC45069
SUMMARY:Frei
DTSTART;TZID=W. Europe Standard Time:20221130T093200
DTEND;TZID=W. Europe Standard Time:20221130T093500
CLASS:PUBLIC
PRIORITY:5
DTSTAMP:20221124T201701Z
TRANSP:TRANSPARENT
STATUS:CONFIRMED
SEQUENCE:0
X-MICROSOFT-CDO-APPT-SEQUENCE:0
X-MICROSOFT-CDO-BUSYSTATUS:FREE
X-MICROSOFT-CDO-INTENDEDSTATUS:BUSY
X-MICROSOFT-CDO-ALLDAYEVENT:FALSE
X-MICROSOFT-CDO-IMPORTANCE:1
X-MICROSOFT-CDO-INSTTYPE:0
X-MICROSOFT-DONOTFORWARDMEETING:FALSE
X-MICROSOFT-DISALLOW-COUNTER:FALSE
END:VEVENT
END:VCALENDAR

Currently, I get

Begin: 2022-11-30T09:30+02:00
Begin: 2022-11-30T09:32+02:00

and this is one hour too early for me ;)