It seems the only difference in my approach is that I regard the BIOS clock setting as sacrosanct.
I set it manually and everything I install uses that setting as reference and does not change it.
In that manner regardless how many OSs are installed the BIOS clock is not changed by any of them.
In truth, if I could lock the BIOS clock separately, I would, to prevent everything except a BIOS edit from changing it.
I have found this approach to be the most suitable for me ..... particularly when I had many many distros installed on the one PC, and even included a few Win installs also (way back when
There are a few different edit points for locale/time zone and I usually find, when the clock is wrong, that I have missed one of them. Truthfully I can never remember the best way to set it up through GUI. It is more a bit of trial and trying to remember every time I install anew.
Hopefully things are getting sorted now for those with wrong time displays.