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.