From what we can see if all goes to plan the servers will be online at 5.00pm PST, this equates to 8.00pm ET and 1.00am GMT, you can find out more here.
Obviously any downtime seriously annoys a large amount of WoW gamers, however you have to remember that Blizzard is doing this to avoid problems in the future. It has to be said that Blizzard’s scheduled World of Warcraft maintenance often overruns, therefore do not be too surprised if the servers are still unavailable after 5.00pm PST.
It is up to you what you do to keep busy while the maintenance is being carried out, why not check out some of our World of Warcraft: Cataclysm posts for all of the latest information.
As we hear of any more updates regarding any other delays we will keep you posted, it may be worth following WoWInsider on Twitter.
Also See: WoW 6.2 patch release time with notes