Today from 11:30 A.M. EST to 5:00 P.M. EST PlayStation Network will be partially inaccessible. That’s about 5 1/2 hours for maintenance. The PlayStation Store, PlayStation Home, and Account Management will not be available to users during this brief time period. However if you would like to play games online during that time you are advised to sign into PSN before the maintenance period starts.
11:30 AM – 5:00 PM EST
8:30 AM – 2:00 PM PT
In Europe, PSN will also have downtime for maintenance from 4:30 P.M. to 10:00 P.M. GMT. Sony also mentions that users may experience additional downtime for testing purposes.