With today's release of Scars of Mirrodin, both Standard and Extended will rotate to their new forms effective immediately. Each year, with the release of the first set of the new block, these two formats will rotate. Up until that point, each new set will be added to these formats.

What leaves Standard? - Magic 2010, Shards of Alara, Conflux and Alara Reborn

What leaves Extended? - Tenth Edition & Time Spiral, Planar Chaos and Future Sight