Your S10 may have two different radios in it. With or without RDS. Here are the instructions on both! They both should have hour/minute buttons! It should be located under the tuning knob!
Press and hold HR until the correct hour appears on the display. Press and hold MN until the correct minute appears on the display. To display the time with the ignition off, press RECALL or HR/MN and the time will be displayed for a few seconds. There is an initial two-second delay before the clock goes into the time-set mode.
The radio may have a button marked with an H or HR to represent hours and an M or MIN to represent minutes.
Press and hold the hour button until the correct hour appears on the display. AM or PM will appear on the display for morning or evening hours. Press and hold the minute button until the correct minute appears on the display. 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 for two seconds until UPDATED and the clock symbol appears on the display. If the time is not available from the station, NO UPDAT will appear on the display.
RDS time is broadcast once a minute. After tuning to an RDS broadcast station, it may take a few minutes for the time to update.