I wont be able to get pokebank now
Btw it came out 4 hours from this post :P
It ends on the 30th of September 2014.
"This Celebi was available to players who accessed Pokémon Bank from December 25, 2013 to September 30, 2014."
"If the player accesses Pokémon Bank before September 30, 2014, they can receive a special event Celebi. This particular Celebi knows Hold Back, an event-exclusive move similar to False Swipe."
Hope I helped :)
September 30th, 2014, just like before it crashed. And the article talks about Europe, but it applies everywhere.
It Began in December with those who have pokebank it will end September 30 of 2014
to learn how to get your Celebi watch this:https://www.youtube.com/watch?v=V7WBorGUrWY