Set the clock on 91 gmc truck. Battery was replaced and I need to set the correct time.

Setting the Clock for All Systems Except AM-FM Stereo with Compact Disc Player
Press SET. Within five seconds, press and hold SEEK until the correct minute appears on the display. Press and hold SCAN until the correct hour appears on the display.

Setting the Clock for AM-FM Stereo with Compact Disc Player
Press SET. (The radio may be on or off.) Within five seconds, press the SEEK right or left arrow until the correct minute appears on the display. Press and hold SCAN until the correct hour appears on the display.

Hope it helps

Weird, are you resetting the clock and finishing the setting as per your manual. Your navigation zone could be throwing it off, make sure you have correct zone for where you are. press the helpful button, and check video link below.

How to Set Clock and Search Area on 2010 and 2011 GMC full size Navigation

How to Set the Clock on GMC Yukon 2007 2013 2008 GMC Yukon Denali 6 2L V8

DL the opertators guide.
its free for allcars.
google it. " 2002 GMC Sierra 1500 operators guide"
that trick works for all cars made,no need to guess.
if your is lost. RTM

does cigarette lighter work you most likely have a blown fuse in the memory of clock it is part of the stereo but has 2 fuses that function it, power and memory. If its in the radio/clock all presets on radio usually go out to, look for blown fuse.

No sure what model and year Chevy you have but this could be an indication the battery is getting weak. If this happens when you start the vehicle the battery voltage drops low enough to cause the clock to lose it's setting. I would test or have the battery tested and replace it if it fails.

There are two procedures and it depends on whether your radio has the option of Auitomatic Tone Control. Here are both ways, with and without Auto tone Control.

Setting the Clock for Systems without

Automatic Tone Control

Press SET. Within five seconds, press and hold the

SEEK right arrow until the correct minute appears on

the display. Press and hold the SEEK left arrow until the
correct hour appears on the display.

Setting the Clock for Systems with

Automatic Tone Control

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 clock 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.

For my 91 GMC I didn't have to hold the set button just click it and "set" showed up beside the time and I was able to change it! Thanks for the help!!

I found this solution already was answered by: chavezemail
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Owners manual: 3-10:

Setting the Clock for Systems with HR and
MN Buttons
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 clock 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.

Setting the Clock for Systems with
SET Button
Press SET. Within five seconds, press and hold the
SEEK right arrow until the correct minute appears on
the display. Press and hold the SEEK left arrow until the
correct hour appears on the display.

It really depends on the type and model of your radio. Below is the generic clock set proceedure for the most popular radio at that time.
Hope this works for you.
Regards,

To set the clock, just:
Press the SET button. The word SET will light up in the VF display.
Within 5 seconds, press and hold the SEEK button until the correct hour
appears on the display.
Then, press and hold the SCAN button until the correct minute appears
After you set the time, the word SET will remain in the VF display for a
on the display.
few seconds.

31 sounds about right for a sierra and the clock settings are in the menu. Hit menu then you have a small round knob to advance the hour or you have two small buttons in the lower right hand corner of the radio.