The US Servers will come down on Thursday, February 28, 2013, at 7:00 am Pacific* for an update. The expected downtime is one hour. The EU Servers will come down at 9:00 pm Pacific* on 2/28 (5:00 am London* on 3/1). The estimated downtime will be 2 hours.
Update Notes will be posted here when available: Game Update Notes.