The program runs great under the mega65. Could you access the date in C64 mode?
You could adapt this program to work from C64 mode, yes. "Left as an exercise to the reader".
There are still problems in the configuration menu. In my opinion the time is not read correctly from the RTC. After 11:59.00 comes 32:00.01 ? After 23:50.00 comes 24:00.01 ?
Once the menu has been saved you can no longer access the device. Only after switching it off and on again everything works again. Maybe Paul has a good idea again.
Yes, this is because the values are BCD, with $20 meaning PM. Log an issue on github.com/mega65/mega65-core/issues. It wouldn't be too hard for someone with some 6502 skills to find and fix.