The PlayStation Network will be partially down for about seven hours on Thursday, November 7th for scheduled maintenance. The window was announced on the PlayStation Community Forums and is scheduled from 11 A.M EST to 7 P.M. EST.
The PlayStation Store, PlayStation home and Account Management will unavailable to users during the seven hour window. If you want to play games online or use apps that require the internet, you are advised to sign into the PSN before the maintenance window and stay logged in.
According to the European PlayStation Community forums, the PlayStation Network in that region will be down for a little longer. The 11-hour maintenance window is scheduled for the same day from 2 P.M. GMT until 1 A.M GMT the following day. There may be additional downtime for testing purposes as well.