From the Facebook page.
Thank you for all your help in today's Stress Test!
We will be conducting a Stress Test on Friday, August 10 from 4:00 PM PACIFIC Time to 8:00 PM PACIFIC Time.
REMEMBER: We will be actively working on the game during the event, so you might experience connectivity problems or discover features that are not working as designed. Any issues you experience are a result of the rigorous conditions of the stress test, and are in no way representative of the state of the game at launch. By participating in this stress test, you're helping us make Guild Wars 2 a better game. Thanks for your cooperation-we'll see you in-game!
* Stress Tests are open to those who have PRE-PURCHASED the game.
* Characters will not be wiped for tomorrow's Stress Test.