I've been running slackware forever, and this situation often comes up; I admit it may have happened to me more than once!
however, it may provide insight as to correcting your issue.
openSUSE is an open, free and secure operating system for PC, laptops, servers and ARM devices. Managing your emails, browsing the web, watching online streams, playing games, serving websites or doing office work never felt this empowering. And best part? It's not only backed by one of the leaders in open source industry, but also driven by lively community.
I've been running slackware forever, and this situation often comes up; I admit it may have happened to me more than once!
however, it may provide insight as to correcting your issue.
Wild guess, maybe YaST actually has a section for that.
But i'm sure you can correct the hardware clock and or tell your system what to save there.