Can you reproduce this problem now? I’m not seeing it… wondering if that’s related to the time, or my timezone. Where do you live?
I think there’s a problem in there somewhere related to daylight savings, but it’s complex. Last time I dug into it I think I ended up convincing myself that it was working correct (from a certain perspective at least), but seems the perspective should match up with whatever Reminders.app thinks, so maybe need some more changes.
Anyway please let me know what your time zone is and if you can still repeat the problem.