Switching from AM to PM or vice versa on manually recording feature

I was trying to record a morning show (AM) using the manual recording feature, but I was doing it in the evening (PM).  I was able to enter the channel, choose the day then enter the start and stop times, EXCEPT for changing PM to AM.  If you are setting up the schedule in the evening, that field always shows "PM" and there does not seem to be a way to change it to "AM".  If you are setting up the recording in the morning, then that field shows "AM" and there does not seem to be a way to change it to "PM".  Does anyone know how to change it from AM to PM or vice versa?  I pressed every button on the remote and nothing worked.