Users started to noted a bug in iOS 6 affecting the 'Do Not Disturb' feature on New Year's Day. This is another bug affecting iOS with New Year's Day as a similar thing happened with the daylight savings bug. That bug delayed alarm clocks worldwide causing people to be late for work and etc.
Apparently every change with iPhone's calendar and clock has some bug in iOS. The problem now is in scheduled time feature which needs to turn 'Do Not Disturb' feature off at some time, but apparently it doesn't. The only fix is to turn the setting off.
"I am in Japan so it is 2013, and I am finding that my iOS devices (iPhone 4 and iPad 2) are showing "Do Not Disturb" even though it is outside of the time I set for them. Not sure if this is related to the new year. Reloading the devices does not help and the software is up-to-date," said Spacesamurai, a MacRumors forum member.