A new update has been made on the Playstation blog which many people will be glad to read:

We are aware that the internal clock functionality in the PS3 units other than the slim model, recognized the year 2010 as a leap year. Having the internal clock date change from February 29 to March 1 (both GMT), we have verified that the symptoms are now resolved and that users are able to use their PS3 normally.

If the time displayed on the XMB is still incorrect, users are able to adjust time settings manually or via the internet. If we have new information, we will update you through the PlayStation.Blog orPlayStation.com.

We apologize for any inconvenience this may have caused.