I saw several discussions to the effect that do-not-disturb scheduling did not work for the first week of January 2013. I did in fact see that bug on both my iPhone 4S and my iPad 3.
However, it still appears to be not scheduling on both of my devices, even through to today, on the 11th. Is anybody else still seeing this?
View the Correct Answer -Not-Disturb Mode Still Not Scheduling Even After 1/7 in iPhone errors Question , iPhone 4S Support