A have a dual boot system: Ubuntu and Arch. Ubuntu was installed first. A while after installing Arch, I've set up its clock because it was 8 behind my current time zone (my time zone is gmt +8). I don't remember the actual command, something like
date --set "xxxxxx". However, I do remember that I specified the time zone during its installation (gmt +8, Hong Kong). And when I checked
sysclock and it showed the real time in my time zone.
In Ubuntu the time zone remained the same - gmt +8. That being said, after setting up the clock in Arch I found out that the clock in Ubunutu was 8 hours behind the actual time. But! The time zone was still the same - gmt +8. So now in both systems the time zone is the same (Hong Kong) but the time is different in 8 hours. What's more that the clock in Ubuntu was changed by itself when I changed the clock in Arch.
What do I do about that?
sudo hwclock --show shows the same time on both systems.