There is a Forum Post where the recommendation is made to sync your Wellue O2 ring with your PC. In the latest version of the PC software there is just a button marked "Sync time..." No details are shown and there don't appear to be any options to choose.
Well my O2 ring was pretty close to the correct LOCAL time here, showing me wearing the ring from about 9-10PM until 5-6AM the next morning. Thinking it could hurt to keep the time in sync with the PC, I clicked the button.
BIG MISTAKE.
My O2 ring now thinks that I'm going to bed at 0700 in the morning and waking at 1500 the same day.
I haven't yet worked out how to put things back to the previous settings, but have reached out to Wellue to help fix this issue and also correct any anomalous data.
So CAVEAT USER. If it ain't broke, or you're not sure; Leave it.