GMC 2010 Sierra Owner's Manual page 311

To change the time default setting from 12 hour to
24 hour or to change the date default setting from
month/day/year to day/month/year:
1. Press the button and then the softkey located
below the forward arrow tab. 12H, 24H, the date
MM/DD (month and day), and DD/MM (day and
month) displays.
2. Press the softkey located below the desired option.
3. Press the button again to apply the desired
option, or let the screen time out.
MP3 Radio with a Six-Disc CD Player
To set the time and date:
1. Turn the ignition key to ACC/ACCESSORY or ON/
RUN, then press the
2. Press the MENU button.
3. Press the button to display HR, MIN, MM, DD,
YYYY (hour, minute, month, day, and year).
4. Press the softkey located under any one of the
tabs to change that setting.
O
button to turn the radio on.
5. To increase the time or date, do one of the
following:
Press the softkey below the selected tab.
¨
Press the SEEK button.
\
Press the FWD button.
Turn the knob clockwise.
6. To decrease the time or date, do one of the
following:
©
Press the SEEK button.
s
Press the REV button.
Turn the knob counterclockwise.
To change the time default setting from 12 hour to
24 hour or to change the date default setting from
month/day to day/month:
1. Press the MENU button and then the softkey under
the tab.
2. Press the softkey located below the forward arrow
tab. 12H, 24H, the date MM/DD (month and day),
and DD/MM/ (day and month) displays.
3. Press the softkey located below the desired option.
4. Press the MENU button again to apply the desired
option, or let the screen time out.
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