From the programming extension (usually 100) with the handset in the cradle

>Press the FEATURE button

>Press 9 #

>Enter the hour (01-12) and minute (00-59)

>Press the Recall key to change the AM/PM Setting

>Press the Hold Key and continue if you want to change the calendar setting

>Press SPKR or hang up. The correct time should display

 

Your time should now be changed