I had to reinstall Tumbleweed recently, and I think I made a bad choice in the installer when asked if my BIOS clock was UTC or not. Honestly, at the time, I wasn’t sure.
When I boot my laptop, the clock is usually correct, but when I get back from lunch it shows 2 hours later than it really is. My timezone is UTC+2.
How do I fix this?
I’ve been running slackware forever, and this situation often comes up; I admit it may have happened to me more than once!
It’s Slackware Specific
however, it may provide insight as to correcting your issue.