Can I reset my system back to a specific date?

Yes, there is no "System Restore" as in the Windows method of tracking changes on a system and reverting to a specific time. I don't believe that the Windows program has ever really been all that effective or anywhere near as good as the GoBack program was.

Apple provided Time Machine for you to be able to restore your files, or even the entire system to a specific date, but the restore history should be on a different drive that the boot drive, in case the boot drive has failed and you need to restore to a new one.

Are you trying to restore your System or the User account, or both?

I'm not sure that I entirely understand what you mean. If you're interested in setting the clock back for some reason, that would be achieved in System Preferences -> Date & Time. If you're trying to revert the entire system to the state it was in on a specific day, then you can only do that if you are using Time Machine (or some other method) for backing up your machine.

Yes, if you have been using Time Machine. From the Time Machine menu bar item, you can restore any file to an earlier version. If you boot from your Snow Leopard install DVD, you can go to the Utilities menu and restore the entire system to a particular time from your Time Machine backup drive.