GM Service Manual Online
For 1990-2009 cars only

The radio could 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. 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 RDS TIME displays. To accept this time, press and hold the hour and minute buttons, at the same time, for another two seconds. If the time is not available from the station, NO UPDAT (update) displays.

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.