The datamined Anniversary Day special has been activated, and all characters in Diablo 3 are now rolling with a bonus to their Magic Find and Experience. These bonuses are exactly as if you had a permanent Fortune Shrine and Enlightened Shrine, adding 25% bonus to both stats.
The Magic Find bonus is 25% added to your total, and since it works like a Fortune Shrine it can exceed the 300% hard cap from Paragon + item bonuses. My Monk was running 425% in an MP1 farming game once I was fully stacked, when the usual max on MP1 is 400%. And I found eleventeen legendaries! (IMHO 25% is a pretty meek bonus. We’ve been waiting all year. Why not 100 or 200%?)
The experience bonus is better. Just like an Enlightened Shrine it’s granted on the Nephalem Valor + Multiplayer side of the newly-multiplicative equation, which and it adds to those and multiplies all of your EXP bonus from Monster Power and equipment.
The screens below show a brand new Wizard I made to test. She was sitting at 25% to Exp and MF on MP0, but when I restarted the game on MP10 she was at 25% MF and all the way up to +275% Exp, thanks to the 1.25% x 200% for the Monster Power setting. (I dinged to level 2 at the start of the zombie fight outside the town gates, and dinged to level 3 after killing two of the zombies in the Inn, putting her already a full level ahead of normal MP0 pace.)
Your character does not show a shrine bonus, just the special buff icon, so presumably you could double either or both bonuses by hitting the appropriate shrines. And then zoom zoom for two minutes of bliss.
Update: Blizzard has updated about this bonus, and there’s good news; it runs until next Tuesday, so you don’t have to sit up playing all night in a mad quest for Paragon 100. Quote:
To celebrate this milestone and the community that made it possible, we’re giving away free buffs! (Who doesn’t like free buffs?) Players who log in to defend Sanctuary between May 15 and May 21 will receive a 25% boost to their Magic Find and +EXP stats. The buff is only available while logged in to the game, but it will apply to all characters as well as stack with other similar bonuses — the +EXP bonus will stack multiplicatively and the Magic Find bonus will stack above the 300% cap!