Not really a "bug" as in code not working properly, but the 12-hour window for Overseer quest rotations changes with every downtime. Can't this just be made a specific UTC value and be done and over with? I don't really care what UTC is chosen, just being static would be nice.
I was wondering if the timers just stop counting down when the servers are offline but start counting down again when the servers are up but locked. The rotation time seems to drift later by 30 minutes to an hour after the patch every month. While it's annoying, maybe it spreads the annoyance around for players in different time zones.
The rotation timer drifts on a daily basis. Not sure if there is additional drift due to patches. For me, this last patch had negligible drift in addition to the expected daily drift. I believe that when the timer runs out it runs the rotation script (which may take 30-60 seconds) and then starts the 12hr timer after, instead of 12hr from when the first timer ran out.