I got a new hard drive put in recently as the old one suddenly stopped working, and my computer's clock has been weird. I will set it to the right time, only to find in a couple of days it is suddenly 3 hours off. I set it back to the right time and in a few days, it's off again. Why is this? It is realyy annoying, especially the time when I thought it was 3 hours earlier than it really was and was nearly late for work.

 

Thanks.