http://entry.ffxiv.com/beta/detail_na.html

Under the heading "Beta Test Schedule"

The beta test will be divided into four phases. During phase 1, the game will only be available for a few hours on specific days, but availability will be increased in subsequent phases. A more detailed testing schedule will be posted on the Beta Tester Forum.
That is all of the official information we have.

*edit* Steve beat me