Serialized EXDATE is unpermitted PERIOD value type when originated as System.DateTime

[jvraines]

This code

Calendar myCal = new Calendar();
CalendarEvent myEvent = new CalendarEvent {
    Start = new CalDateTime(2024, 12, 1, 12, 0, 0),
    End = new CalDateTime(2025, 1, 1, 18, 0, 0),
    RecurrenceRules = new List<RecurrencePattern> {
                            new RecurrencePattern {
                                Frequency = FrequencyType.Daily
                            }
                      }
};
myEvent.ExceptionDates.Add(new PeriodList { 
    new CalDateTime(2024, 12, 25)
    new CalDateTime(new DateTime(2024, 12, 26))
});
myCal.Events.Add(myEvent);
Console.WriteLine(new CalendarSerializer().SerializeToString(myCal));

produces

BEGIN:VCALENDAR PRODID:-//github.com/rianjs/ical.net//NONSGML ical.net 4.0//EN VERSION:2.0 BEGIN:VEVENT DTEND:20250101T180000 DTSTAMP:20240901T232258Z DTSTART:20241201T120000 EXDATE:20241225T000000,20241226/P1D RRULE:FREQ=DAILY SEQUENCE:0 UID:d65129f0-d00c-46d1-a7d2-81a73a41990d END:VEVENT END:VCALENDAR

The first excluded date is an acceptable DATE-TIME value type. The second, however, is a PERIOD value type which is not permitted by the EXDATE spec.