the time goes forward 5 minutes each week

Wow, thank you so much for tracking this down - that's perfect!

The first change looks harmless if the SYSCLK_FREQ is divisible by 1000

Actually, SYSCLK_FREQ = 1048576 (it's a bit confusing as it's different to STM32 since it's just the precision used for storing time values)

So it'd be losing 576 out of 1000000 which is almost exactly what I'd worked out above at 496.

I had the time jump by hours

I would have said that was maybe the issue with the RTC being reset and the re-loaded on reboot, but having seen that I guess it's not the case!

I've just pushed a change so if you try a Cutting Edge build now it should be fixed.

Sorry about that! I'll do some tests here and assuming it's fixed I'll push out a 2v23 release