As reported earlier iOS 6's 'Do Not Disturb' feature, which basically allows a user to silent all calls, messages and notifications, reportedly went kaput for many users on New Year's Eve. Unsuspecting iOS 6 users found the scheduling of DND to be completely off track. A few of them found DND running on the phone without being switched by the user, while it wouldn't shut off for others.
Apple's support article confirmed that iPhone, iPad and iPod touch were all impacted by the issue, which all but confirms that it is a core iOS 6, not limited to a single device.
Apple also suggested users should manually turn notifications off and on as a workaround until 'normal service' is resumed post January 7.
After January 1st, 2013, Do Not Disturb mode stays on past its scheduled end time.
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.
To turn off the scheduling feature, tap Settings > Notifications > Do Not Disturb and switch Scheduled to Off.