Silly question - but you did make sure to hit the Save button afterwards, right?
Yep, auto-detect and save, it just sets it the correct time but the day before.
The closest I can get is the correct date but an hour behind the correct time, by time-offset 23.
If I try time-offset 24 (which would bring it in line perfectly) I'm told that the "The time offset is out of range" ... so close!