#87 First Occurrences Not Time Zoned Properly

[Paul Neary]

I am trying to get occurrences out of a homemade iCal, but in some cases, it seems that the first two occurrences have an incorrect UTC property, and I believe this is because they have a null TimeZoneObservance, despite the iCal being properly set with a time zone. Here's the code:

    static void Main(string[] args)
    {
        IICalendar iCal         = new iCalendar();
        iCal.AddTimeZone(TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time"));
        string tzid             = iCal.TimeZones[0].TZID;           // Need this when we make iCal date/time objects

        IEvent Evt              = iCal.Create<Event>();
        Evt.Summary             = "Test";                           // This is just a dummy name
        Evt.Start               = new iCalDateTime(new DateTime(2012, 9, 28, 12, 00, 00, DateTimeKind.Unspecified), tzid);
        Evt.End                 = Evt.Start.AddMinutes(30);
        Evt.Start.AssociatedObject = Evt.End.AssociatedObject = iCal;
        Debug.Print("Evt.Start={0}, Evt.Start.UTC={1}", Evt.Start, Evt.Start.UTC);

        var iCalFrom            = new iCalDateTime(new DateTime(2012, 9, 28, 12, 00, 00,  DateTimeKind.Unspecified), tzid);
        var iCalTo              = new iCalDateTime(new DateTime(2013, 8, 28, 12, 00, 00,  DateTimeKind.Unspecified), tzid);
        iCalTo.AssociatedObject = iCalFrom.AssociatedObject = iCal;

        Evt.RecurrenceRules.Add(new RecurrencePattern("FREQ=MONTHLY;INTERVAL=1;BYMONTHDAY=28;WKST=SU;COUNT=10;"));
        IList<Occurrence> Occurrences = Evt.GetOccurrences(iCalFrom, iCalTo);

        foreach (var o in Occurrences)
            Debug.Print("{0} (UTC={1})", o.Period.StartTime, o.Period.StartTime.UTC);
    }

Here's the Debug.Print output:

9/28/2012 12:00:00 PM (UTC=09/28/2012 16:00:00)
10/28/2012 12:00:00 PM (UTC=10/28/2012 16:00:00)
11/28/2012 12:00:00 PM Pacific Standard Time (UTC=11/28/2012 20:00:00)
12/28/2012 12:00:00 PM Pacific Standard Time (UTC=12/28/2012 20:00:00)
1/28/2013 12:00:00 PM Pacific Standard Time (UTC=01/28/2013 20:00:00)
2/28/2013 12:00:00 PM Pacific Standard Time (UTC=02/28/2013 20:00:00)
3/28/2013 12:00:00 PM Pacific Daylight Time (UTC=03/28/2013 19:00:00)
4/28/2013 12:00:00 PM Pacific Daylight Time (UTC=04/28/2013 19:00:00)
5/28/2013 12:00:00 PM Pacific Daylight Time (UTC=05/28/2013 19:00:00)
6/28/2013 12:00:00 PM Pacific Daylight Time (UTC=06/28/2013 19:00:00)

Notice that the first two don't show a TZ from the ToString(), and while the local time is correct, the UTC is not. I believe that this happens for the occurrences before the first DST to STD time transition. This also only is a problem when I use a time zone other than the local time zone and a time zone that has DST. Thus if I use "Eastern Time Zone" (where I am) or "US Mountain Time Zone" (for Arizona, which does not use DST), I don't see this problem.