The PlayStation Network will be offline for three and a half hours for scheduled maintenance beginning 9am PT / 12pm ET / 5pm GMT on February 12, Sony announced today.
During this time, you'll be unable to access the PlayStation Store, PSN account management, PSN account registration, entertainment apps, and online gameplay. However, if you sign into your account before the maintenance begins, you'll be able to play games online and use apps such as Netflix.
Throughout the downtime, you'll still be able to collect trophies, but they won't appear on your profile until the network is back up.