On Thursday 28th October PlayStation®Network will be undergoing maintenance. This maintenance will occur from around 15:30 (BST) and is expected to finish at around 00:30 (BST) on Friday 29th October.
During this time you will not be able to access services such as the PlayStation®Store, Account Management or Registration.
So log in into the PSN before 15:30 (BST)!
So you can still play online.