Apple has acknowledged the Do Not Disturb bug in iOS 6, but instead of promising an update to fix it has told users that it will fix itself on Monday.
It doesn’t explain why or how it will fix itself, leaving developers and reporters to come up with a variety of possible explanations.
The most common, and likeliest, explanation relates to the possible (probable?) use of the ISO week date system (formatted as YYYY), rather than Gregorian calendar weeks (yyyy), somewhere in the scheduling code for DND. It’s explained here by Richard Gaywood (note the update at the top of the post where Gaywood explains an error in the explanation. Nevertheless, it seems likely that the difference between yyyy and YYYY is at the root of the bug).
In the ISO week date system, the first week of the year is the week which contains the 4th of January and the week which contains the first Thursday of the year. That’s this week. So ISO week 1 2013 began on Monday. But Monday’s Gregorian calendar date was 31/12/12. Next Monday, the 7th, is the first first day of the week in which the Gregorian and ISO weeks will both have a date with the year 2013.
The Guardian reports here that testing Apple’s assertion by setting an iOS device’s date to 7th January does indeed fix the bug.