Those are invalid times. Your date time validation should report an error to the user. For recurring scheduled reminders, I would remind them at 1:00AM along with explanation why they are getting that reminder early. There is no way to automatically handle this to my knowledge. So it's an edge case one must handle.
You could argue that the case of the clock jumping forward is an invalid time. But the case of the clock jumping back is in fact a valid time, even if it is non-unique.
