As a fairly consistent rule you can count on these kinds of things opening at 10am of that regions’ release time from here on out. In the case on the NA realms (which includes LatAm and Oceanic) it’s Pacific. The first wing of Raid Finder and Mythic Highmaul will open today at 10am PST.
Similarly, tomorrow EU first wing of Raid Finder and Mythic Highmaul will open at 10am CET.
Specifics on dates for each difficulty/wing can be found in the Highmaul Raid Schedule post.
Edited by Bashiok on 12/9/2014 8:20 AM PST
Adopt Argi Now and Support the American Red Cross
Bring home Argi today and support Ebola relief in the process. This impossibly cute little new pet will jump into your heart and nibble at your Blue Woolen Socks. She’s ready to help guide you through the savage lands of Draenor, climbing, swimming, and running wherever you go. For every Argi pet purchased between December 3 and December 31, 100% of the adoption fee ($10 in the US; pricing varies by region) will be donated in support of the American Red Cross to assist in Ebola relief efforts in Africa.
We will be performing scheduled maintenance beginning on Tuesday, December 2, at 3:00 AM PST and we expect the service to be available again at approximately 11:00 AM PST. During this time the game and many web services will be unavailable.
Thank you for your patience.