GMC 2008 Envoy - Manual (Page 200)

Your vehicle may have a feature called Retained
Accessory Power (RAP). With RAP, the audio system
can be played even after the ignition is turned off.
See Retained Accessory Power (RAP) on page 2-22
for more information.
Setting the Clock
The radio may have a button marked with an H or HR to
represent hours and an M or MN to represent minutes.
Press and hold the hour button until the correct hour
displays. AM or PM displays for morning or evening
hours. Press and hold the minute button until the correct
minute displays. The time can be set with the ignition
on or off.
To synchronize the time with an FM station broadcasting
Radio Data System (RDS) information, press and hold
the hour and minute buttons at the same time until
UPDATED and the clock symbol appear on the display.
If the time is not available from the station, NO UPDATE
or NO UPDAT will appear on the display.
RDS time is broadcast once a minute. After tuning to
an RDS broadcast station, it could take a few minutes
for the time to update.
Radio(s)
Base Radio Shown, Bose ® Similar
3-66