That is typically a symptom associated with a bad CMOS battery. Usually they last 3-4 years at least, but every now and then you get someone who will get a brand new system that has a dead battery.
If the thing is under warranty, have Toshiba replace it. Otherwise, you need to crack open the system, take the battery out, and go looking for a suitable replacement. Shouldn't cost you more than $10. It's just a simple coin cell battery.
I have a Toshiba laptop running Windows 7 home edition. I have noticed that my clock does not keep time, often advancing. I often put the laptop on hibernate...sometimes sleep. I do reboot about twice a week. Is the sleep/hibernation causing the clock problem and why should it? Is sleep better than hibernate?