iOS 4.1: Repeating alarms may trigger incorrectly before or after DST change
iPhone 3G, iPhone 3GS, iPhone 4, iPod touch (2nd generation), iPod touch (3rd generation), iPod touch (4th generation)
In some regions, shortly before or after the daylight saving time (DST) change, repeating alarms created in the Clock app may work incorrectly.
To resolve this behavior for existing alarms, set the repeat interval to Never. You will need to reset these alarms for each day you need them.
After November 7th, 2010, you can set your alarms to repeat again.