DTEND DATE value is not reckoned exclusively

[jvraines]

A loaded event containing the property

DTEND;VALUE=DATE:20241128

is returned by GetOccurrences(new DateTime(2024, 11, 28)). This is contrary to the spec, which says

The "DTEND" property for a "VEVENT" calendar component specifies the non-inclusive end of the event.

I understand this to mean that an event which ends by 0000 hours on a date is not an occurrence on that date.

[minichma]

Can you provide a reproducer and more details on the version you are using?

On the current main branch the following test succeeds:

    [Test]
    public void TestGetOccurrence_DtEndExcluded()
    {
        var ical = """
            BEGIN:VCALENDAR
            VERSION:2.0
            BEGIN:VEVENT
            DTSTART:20241201
            DTEND:20241202
            END:VEVENT
            END:VCALENDAR
            """;

        var calendar = Calendar.Load(ical);
        var occurrences = calendar.GetOccurrences(new CalDateTime("20241202")).ToList();

        Assert.That(occurrences, Is.Empty);
    }

[jvraines]

Certainly. I am using Version 4.3.1 in .NET Framework 4.8.
Your test works for me but this string produces the bug when supplying 20241128 to GetOccurrences.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:Video Wall
BEGIN:VEVENT
UID:VW6
DTSTAMP:20240630T000000Z
DTSTART;VALUE=DATE:20241001
DTEND;VALUE=DATE:20241128
SUMMARY:New home speech.mp4
COMMENT:New location announcement; may need update before Thanksgiving
END:VEVENT
END:VCALENDAR

[minichma]

Oh yes, now I can reproduce it. The problem disappears when setting DTSTART to 20241101. Probably the problem is related to the a DST change between DTSTART and DTEND. Assume, you are located in a timezone with positive offset and DST change in October like CET. Can you confirm? The lib incorrectly considers DTEND at 20241128 at 01:00 hours.

@axunonb FYI, likely related to faulty involvement of the local time zone.

[jvraines]

Good sleuthing! Yes, I am in Pacific Time Zone with a summer offset of -7 hours and a change back to Standard Time on the second Sunday of November. Yet another reason to loathe the time-change kerfuffle.

[minichma]

@axunonb Btw., this is the full reproducing test case, just in case you can use it in #658.

    [Test]
    public void TestGetOccurrence_DtEndExcluded()
    {
        var ical = """
            BEGIN:VCALENDAR
            VERSION:2.0
            PRODID:Video Wall
            BEGIN:VEVENT
            UID:VW6
            DTSTAMP:20240630T000000Z
            DTSTART;VALUE=DATE:20241001
            DTEND;VALUE=DATE:20241128
            SUMMARY:New home speech.mp4
            COMMENT:New location announcement; may need update before Thanksgiving
            END:VEVENT
            END:VCALENDAR
            """;

        var calendar = Calendar.Load(ical);
        var occurrences = calendar.GetOccurrences(new CalDateTime("20241128")).ToList();

        Assert.That(occurrences, Is.Empty);
    }

Created the related ticket #660 which discusses the same topic for the case that DTSTART/DTEND are specified with a time zone reference.

[Edit] fixed c&p error