It does say, as you can see in the following quote:
Mod Scorpio
said
:
There will be plenty of ways you can donate and get involved in all the action. PLUS, it wouldn’t be GameBlast without a Double XP Weekend, would it? Of course not!
From 12:00 UTC on 23rd February until 12:00 UTC on 26th
February you can level-up at double the speed. Now’s the time to start preparing. What’s your next 99?