Weekly quests, or weeklies, are repeatable quests that can be acquired and completed once/twice per week. First introduced with patch 3.1.2 in the combat zoneWintergrasp, they tend to have significantly better rewards than other repeatable quests.
The new weekly quest becomes available—at the start of the day—every Tuesday for US servers and Wednesday for EU servers, after the weekly server maintenance.
A special case were the Wintergrasp quests, which also reset every five days, in addition to the weekly reset. This is no longer the case as of patch 3.3.2.
Weekly PvP quests
The first zone to have PvP weeklies was Wintergrasp.
One of the following quests will be randomly selected during each Icecrown Citadel raid ID. The quests involve completing extra objectives during the instance, often by doing something different during a boss fight.
Patch 3.3.3 (2010-03-23):Wintergrasp weekly quests introduced. All weekly quests will now reset during each region's scheduled maintenance, rather than at a single global time.