At&t cl82401 date and time

the battery inside is dead, this will cause the date to be wrong;
just like the same thing on real computers.
the clock in side is RTC time clock chip and needs power to work.
power = battery.
#1 all time failure on any portable device is batteries.

you could ask them directly at
https://buy.garmin.com/en-US/US/p/8523

There is not a lot of info, but I'm gonna go with the choice of a laptop, since you say "new battery". There is also another battery in the motherboard, also, you need to set the date from within the BIOS, if you don't set it from the BIOS it will always revert back to the date of manufacture.

This indicates the BIOS battery is flat and therefore cannot store the correct date and time in the BIOS. You need to install a new BIOS battery and then go into the BIOS setup to set the Date & Time.

Please update the phone software or either restore it to factory settings.

Kindly revert back for any further clarification

To go settings, then general settings. you will find date & time there.

Please update it.

Kindly revert back for any further clarification

you need to remove the cover with the power off. inside you will find to chips in caddes. remove the both. remebring where they went. un plug the hard drive/s and put power back on without the chips in should come on screen saying systerm error. turn off put avery thing back in and turn on now should start up and ask you time and date program it in and it will rest. should start up with the date and time you set now.

Press Menu and select the Setting Menu. Navigate down to "Date Adjust" and press Right-arrow, and the Date Adjust screen will appear. Navigate around and change the settings. Press OK when done.

If you've misplaced your manual, you can download one from the manufacturer's web site at http://www.pentaximaging.com

My machine goes this way-
Hit time/date button.
then enter in date (ie) 11.16.2009--INCLUDE DECIMAL!!!
Then hit time/date button again,

I am still working on the time issue, I just cant seem to remeber, I know it is done off military time.

I have the same problem. I cannot believe I wasted $70 this stupid phone. No more RCA ever.

Does the date/time revert back only after you send/receive a call? If so, it's possible that it's trying to pull the local time from your SIP provider, and either that's not working as it should, or their server has the wrong dame/time set.