I recently put together a rig, and I've been having nothing but trouble with the clock.
With all the installing and updating at the time, I don't quite remember, but I believe the clock was fine for the first few weeks after the build. The last few months since however, the time is never correct, either in Windows or BIOS. Also since this clock business started happening, the power light - which used to slowly flash when I put the computer to sleep - stays on.
If I watch Netflix for an hour, the clock doesn't advance - or at least nothing close to the full hour. If I play a videogame, same deal. Sometimes even just browsing the internet it seems to drop a few minutes here and there. If I put the computer to sleep, it wakes up with the same time it had when it went to bed. If I set the clock to the right time, wait a few minutes, then reset, it will start back up with the time I first set it to.
Going to the command prompt and checking 'time' gives me the same time I have in Windows, so BIOS actually has the wrong time too. If I update to some internet time, it updates just fine and runs for awhile. Lately though, it won't let me update by windows time server, so I switched to one of the nist servers. Now neither the nist server nor the windows server will work, so I have to use nist-a.
I have no idea what's going on.
Battery was my first and only guess. I pulled it out and the voltage checks at a solid 3.3V. I pulled the battery from my years old board that ran just fine and it measured at 2.8V, so I don't believe the battery is the issue.
I did find a solution, but can't remember 100% what it was.
I think I found something was wrong with the BIOS clock, like it was set to an invalid value or something. Whatever it was I remember being subtle, but looking at the settings information you could tell something was wrong. I think when you looked at the BIOS overview, it had a time but the seconds weren't counting. But when you went to change BIOS settings, the time field was blank. If you fill in a time and save it, then go back to the overview, the seconds will now be counting, and the time should be OK after that.
It was quite some time ago, so sorry for the vague and possibly unhelpful post. Good luck.