I have a GE DIgital Messaging SYstem 5.8 GHZ 25942EJ3-C and cannot re-set time Please help

Try this:
1.) Make sure the answering system is on.
2.) Press flash/answerer/call waiting button on the handset to enter answerer remote mode.
3.) Press key (8) to enter Time/Day set menu using the handset.
4.) To set the Hour, key in (00)-(12), like 08 for 8 o'clock.
5.) To set Minutes, key in (00)-(59), like 15 for 15 minutes after the hour.
6.) To set AM/PM, press the CALLER ID-VOLUME up or down buttons.
7.) To set the day of the week, press the CALLER ID-VOLUME up or down buttons.
8.) Press #PAUSE/ringer button to confirm the setting.

Hope this helps you out! Hal

Program the clock. There are a some buttons on the back of the base unit that sets day of the week, hour, and minute.

here is the link to the user manual.instructions to do that should be in there.
User Manual

My phone was also flashing CL and the 0, after a power outage. After I set the date and time it was fixed. Press the flash button on the handset and use the caller ID buttons to set AM or PM; use the numbers to input the correct time. Then press #. Repeat for setting the day and press # again.