System Date Issue

I have been ruuning vista for just over one year. In that time for no apparant reason the system date sets itself to end of 2085. The first time it happened caused a bit of a panic because processes such as Norton and Windows update which are date related in their update processing go haywire, However nowadays it is fairly obvious what has happened and I merely set the date back and all becomes fine wiith the world again. Has anyone else experince this and does anyone know how to presvent it happening.

When the CMOS battery is about to expire, the time is the first to go. In your case it may be the Date.
If your battery is old, replace it.

Thanks very much for the reply. However a friend did suggest that to me some time back . But my understanding is that the battery powers the clock etc when the PC is switched of whereas in my case the date changes have all occured when the machine as been in use. Also the machine is only just over a year old and there are months in between the few times it has happened. I only started this enquiry because it happened again about an hour ago.

If you boot the computer and the time is wrong its the battery. All computers will lose or gain time when on. Bit different, today, since many are tied into interent time.
If its only once, its just a fluke and not a problem
Make a full anti virus scan
Download and make a full scan with malwarebytes to rule out something more sinister.

Hi Sorry I should have made things a bit clearer. It is not actually losing the date but resetting it to the 31st Dec 2085. It has happen four times in total over the last year. What pointed it out to me in the first place was Norton saying that its 'Virus Definitions' were some 27000 days out of date.

Next time it happens go to search by the start button
Type even viewer
put cursor on the left hand panel, administative and see what it says about the problem

Richard Thanks for that advice. Done as you suggested and very interesting results. I can see all the events for five occasions that occured during periods when the system date has advanced such as the two examples extracts below (I do not recall the 8511 date happening the rest however map to what I remember). The third example below is of the events table around the period when the date changed last night but again I cannot see anything obivious that points to it going to happen. If you have any other ideas any help will be much appreciated but on the other hand the issue itself is now just a minor inconvience that takes two minutes to resolve by resetting the date.
Critical 23/05/8511 15:39:32 Kernel-Power 41 None
Description:
The last sleep transition was unsuccessful. This error could be caused if the system stopped responding, failed, or lost power during the sleep transition.
Error 17/11/2085 17:51:09 CAPI2 11 None

Description:
Failed extract of third-party root list from auto update cab at: <http://www.download.windowsupdate.com/msdownload/update/v3/static/trustedr/en/authrootstl.cab> with error: A required certificate is not within its validity period when verifying against the current system clock or the timestamp in the signed file.
Error 21/08/2011 19:46:04 DistributedCOM 10016 None
Warning 21/08/2011 19:44:33 b57nd60a 4 None
Warning 21/08/2011 19:43:59 WLAN-AutoConfig 4001 None
Warning 21/08/2011 18:03:42 Outlook 25 None
Error 21/08/2011 18:02:37 Service Control Manager Eventlog Provider 7000 None
Error 21/08/2011 18:02:37 Service Control Manager Eventlog Provider 7009 None

If that is indeed the cause, seems to be due to a complete loss of power, from sleep mode, which should not happen.
Check out this tutorial, same for Vista, for any hints
http://www.vistax64.com/tutorials/63567-power-options-sleep-mode-problems.html

Thankyou very much for all your time and effort and the recommended tutorial. I have juggled with the hibernation and sleep settings in the past so I will put them back to the recommended and see what happens. Unfortuately being an intermittant issue that has only occurred every two or three months I shall have to wait and see what happens in the future. But again thanks for your help