With the PlayStation Vita due to hit outside of Japan in February, now would seem a good time to take the PlayStation Network down for some maintenance. So, between 4pm today and 5am tomorrow GMT, that's what's happening.Actually it's technically, "approximately 8am until 9pm PST."
Sony states that:
"PlayStation Network will be offline for routine scheduled maintenance on Thursday, January 19th from approximately 8am until 9pm PST.
"During the maintenance, you will be unable to access the following services:
PlayStation Store on PS3, PSP, and Media Go.
PlayStation Network Account Management.
PlayStation Network Account Registration.
PlayStation Home
Music Unlimited & Video Unlimited services"
"In addition, you will not be able to sign in to PlayStation Network from us.playstation.com.
Users who are already signed into their account on PlayStation Network before the start of the maintenance should be able to stay signed in to their online session, but will not be able to access any of the services listed above. Users who attempt to sign-in to their PlayStation Network account after the start of the maintenance may be presented with the site maintenance notification page if they haven’t signed in recently."
Details over at the US PlayStation blog.