As it did in original World of Warcraft, the Zul’Gurub 20-person raid will have a 3-day reset timer. The ZG reset will be different in each region, and the first reset will occur less than one day after the raid opens at 3:00 p.m. PDT on April 15.
In this region, the first reset for ZG will be at 9:00 a.m. PDT on Thursday, April 16. This will be 18 hours after launch.
Thereafter, the raid will reset every 72 hours as expected.