Square Enix seems to be pretty fond of the social networking tool Twitter as that's just what they used to confirm that Final Fantasy XIV will be entering its open beta phase starting early September. Phase 3 of the closed beta is about to come conclusion some time tomorrow.
"The FINAL FANTASY XIV Beta Test Phase 3 will end on August 25, then move to the Open Beta Test in early September. Get ready!"
The full game will retail on September 30. For those that preorder the collector's edition, they'll be able to access the game 8 days earlier on September 22.
Source: Final Fantasy Union