Arenanet have just announced (via their notice on the official forums) that the Beta Weekend Event Finale is taking place in Metrica province (The Asura starting zone) at 11pm PDT
To find out what that is in your timezone, click here and convert it.
A quick run down of the common time zones:
11pm PDT (American Pacific)
2am EDT (American Eastern)
6am GMT (What timezone is GMT right now?)
7am BST (UK timezone, British Summer Time)
8am CET (Central European time)
For all other timezones, check the above link and convert it to your local time.