Sony has announced that PlayStation Network will be down for maintenance for a few hours tomorrow, February 12. According to Sony, the service will be offline from 17:00 until 20:30 GMT.
During the downtime, players will still be able to play online if they recently logged in on their accounts, although they won't be able to access PlayStation Store. Sony warns that users might still experience some "limited PSN functionality."
Feel free to check the announcement for more details about the maintenance.