Spooncraft

Here’s the official word from Blizzard.

The following realms will be brought down for maintenance beginning at 5:00 AM PST, February 27. All realms should be back up and available for play by approximately 6:15 AM PST.

Agamaggan
Azshara
Baelgun
Dark Iron
Detheroc
Emerald Dream
Greymane
Kalecgos
Lightninghoof
Maelstrom
Malfurion
Moonrunner
Nazjatar
Sargeras
Staghelm
Twisting Nether
Ursin
Wildhammer
[ Post edited by Bornakk ] (src)

It doesn’t seem like a long time at all really, only about an hour and fifteen minutes.