(CNN) -- Not forgetting Sunday morning's time change is hard enough.

But Apple iPhone users in the United States must also remember to delete and then reset their phone's alarm clock -- otherwise they may be an hour late for work on Monday morning.

A glitch in the iPhone's operating system will cause recurring weekday alarms not to ring on time on Monday morning because of the end of Daylight Saving Time, which occurs at 2 a.m. on Sunday in the United States.

The phone's alarm app doesn't recognize the time change and will ring an hour late if users don't go into the program and manually reset the alarms.

Users who depend on the iPhone to wake them up should create one-time alarms specifically for Monday morning, said Apple spokeswoman Natalie Harrison.

(via CNN.com)