You may already have noticed that into the New Year, the Do Not Disturb feature on iOS 6 stays on even after the scheduled time has elapsed. If so, fret not because you’re not alone. Apple has acknowledged the issue via their support page, basically stating that all will be well after Monday, January 7th.
Do Not Disturb scheduling feature will resume normal functionality after January 7, 2013. Before this date, you should manually turn the Do Not Disturb feature on or off.
As a current fix, Apple suggests that you manually turn DND on/off by going to Settings > Notifications > Do Not Disturb and switching Scheduled to Off. A bit of a pain in the rear, but at least it’ll only be for a few more days.
Coincidentally, Apple released a commercial on New Years Day touting the Do Not Disturb feature on iOS 6. In the 30 second ad, Venus and Serena Williams are playing table tennis against the narrator (Jeff Daniels) in a dream, in which he remarks how he won’t be disturbed by calls unless it’s important.
Sadly, this New Year bug will mean that you won’t be disturbed for an entire week unless you remember to manually turn the feature on/off.