The event is being hosted from Aug 13th - September 23rd. How to get:
1.Go to Mystery Gift
2. Go to Get gift via Nintendo Wifi.
3. Wait and then you should get the Members Card (Hacking it is gay....)
4. Go to a Pokemart any kind. You will see a guy in green. Go to him and your REAL not hacked Members Card will be given to you.
5. Go to Canalave. Go above you and you will be allowed in.
I caught my Genuine Darkrai. So glad I didn't use a Masterball.... theres no fun in that. Here is Darkrai's info:
Darkrai - Any nature - Lvl 50
Good luck and have fun