That didn't make much sense to me since I thought manually changing the Windows time would update the BIOS clock as well. Since writing this post it has set the time back by exactly 6 hours. It usually changes by somewhat smaller values like dozens of minutes or a couple of hours at a time, which still isn't clock drift; more like clock jump. Here is what I found in the event log, with the most recent event being at bottom (reverse from event log). 27/09/2013 am The system time has changed to 2013-09-26T.729000000Z from 2013-09-26T.729452500Z.
I synced it with the Internet and decided to reboot to check the time in the BIOS.
Surprisingly enough, the BIOS showed the incorrect time as it was just before I synced it previously. To make the whole situation even more weird, I have the Windows Time service on my netbook set to manual and stopped, which means I have no NTP client running on that machine (I disabled it.) So WHY is the time still being changed by strange intervals?
About 3 months ago I bought myself a beefy desktop computer and simply removed the SSD from my laptop and put it in my desktop to use permanently.
It booted fine; I just had to install graphics drivers.
When I woke up, the clock was off by around six hours!
I thought it was just a one-off or something to do with incorrect daylight savings (although I've never experienced a clock error like that in my life; computer clocks have always 'just worked' for me in all prior cases) so I synced it with the Internet and it was fine.Then I went to bed and slept, leaving the computer on at all times as I always do.I recently got the netbook's left-click button repaired and the repair store replaced the CMOS battery yet again with the exact same results.Prior to this incident, I was using Windows mainly on my laptop.
I cannot explain this any more clearly and it has literally driven me insane.
A few weeks ago my netbook's Windows 8 system clock started changing randomly while it was powered on and being used, so after battling with it for days I gave in and changed the CMOS battery even though I was highly sceptical about that being the issue. If I'm not mistaken, a dead CMOS battery has nothing to do with the running system time after boot, so it simply can't be due to the CMOS battery being flat, not that it should be flat considering the netbook is only 3 years old if I have to put a number on it.