Date on WordPress site over a year out

Just a few hours ago, the date on my wordpress installation changed from the correct date to September 25, 2012… I didn’t install any new plugins or change anything on the site as I was sleeping at the time… just got a few messages from visitors to my site that they were having issues posting comments (it was saying “you are posting too quickly – slow down!” after only making one comment).

I am not sure if this is all related, but I cannot find a way to fix this, and have done many searches in support forums and can’t find an answer. I have removed a lot of plug ins, updated the few I use, deactivated them, but still having the issue. Could this be an issue with my VPS or hosting company, or is it a wordpress bug?

Thanks!