I’m not sure what the community event is, but right now on the US and EU realms all Diablo 3 characters are pulling an extra 50% experience bonus. This is 50% on top of all other bonuses, so if you’re running T6 for 1600% exp bonus, it’s 2400% right now. (And even larger if you’re doing multiplayer, wearing +exp% gear, etc.)
Cash in while the rewards are hot. Mira Eamon isn’t going to kill herself over and over and over again, after all.
Update: A blue post about this promotion went live on the Diablo 3 EU site, informing us it would run through March 24th, but that post vanished shortly afterwards. It later resurfaced on the US site, and includes a helpful tutorial video explaining the system changes in D3v2.