By: Tom Sydney Kerckhove <syd@cs-syd.eu>
ical-recurrence: carry the duration across a mismatched RecurrenceDateTimes [section 3.8.5.2](https://datatracker.ietf.org/doc/html/rfc5545#section-3.8.5.2) @ Value Type: The default value type for this property is DATE-TIME. The value type can be set to DATE or PERIOD. @ Appendix A.1 requires DTEND and DUE to use the value type of DTSTART and requires nothing of RDATE, so an RDATE may hand an instance a value type the event does not use. The instance still has to end somewhere, so carry the duration into the value type of the new start instead of refusing it. A whole number of days becomes that many days as an exact duration. Its inverse rounds up to whole days and never down to none, because a DATE-valued DTEND is exclusive and cannot name part of a day, so a one hour event becomes a one day all-day instance. This also drops StartStartMismatch, which those two arms were the only users of. It described a mismatch between the value type of the original start and of the new one, which is now handled rather than rejected, so the constructor could no longer be produced.