Sony has announced today that the PlayStation Network will be undergoing a scheduled maintenance on January 17, 2013. The scheduled maintenance will be regular one, which means nothing new will be added. Sony has released no other details about the maintenance.
The scheduled maintenance will be starting on January 17, 2013 at 8 AM PT (9:00AM MT / 10:00AM CT / 11:00 AM ET) and will end at 8:00PM PT (9:00PM MT / 10:00PM CT / 11:00PM ET). For those in the EU the times for you are January 17, 2013 at 4 PM GMT to 4 AM GMT on January 18, 2013. During this maintenance you will not be able to access the Store and Account Management, so make sure to sign in beforehand if you want to play online.
Source: US PS Blog.