The official US Puzzle Championship will take place on Saturday August 25, at 1pm EDT, and last 2 1/2 hours. You must be registered to participate. All registered participants will receive a reminder email by August 21.
Unofficial participation is open to all puzzlers world-wide, who may start the test any time before 3:30pm ET on Sunday August 26, and are still limited to 2 1/2 hours for answer submission.
BST (GMT+1) Start/End times in the UK are Sat 25/8/12 18:00 to Sun 26/8/12 20:30 (for completion by 23:00 BST)
A reminder that the the top UK competitor is eligible for a place in the UK 2012 WPC team (details).
If you are not yet registered for the USPC, you should do so asap. Good luck!
edit (25/8/12): "Your time starts when you load the password page." ie, There's no start button - the timer will just start ticking from that point.
This means YOU MUST FETCH THE INSTRUCTIONS PASSWORD BEFORE 6PM (UK) TODAY, since they are on the same page! Otherwise the site will consider you to have started the test.