Maintenance is scheduled to start at 1 AM PST/4 AM EST and end at 11 AM PST/2 PM EST. Given that this is a patch day, it's likely that maintenance will be extended at least once, likely several times, meaning your forays into Icecrown might end up a little later than you expect. Just remember that this is the big one, the one we've been waiting for, and that you can wait a little bit longer.
In the meantime, brush up on what's coming with Patch 3.3 in our big ol' guide.
Patch 3.3 is the last major patch of Wrath of the Lich King. With the new Icecrown Citadel 5-man dungeons and 10/25-man raid arriving soon, patch 3.3 will deal the final blow to Arthas. WoW.com's Guide to Patch 3.3 will keep you updated with all the latest patch news.