Early access >> August 29th

[Tsukino]

The end date for early access is designed to overlap with the release date of the game a little bit to compensate for people getting their packages late. The early access code only lasts until a certain date, at which point you need to have either a retail code or one already activated from 1.0 to continue playing. EA lets you continue playing until the 29th so that you have until that time to register your retail code.

If they didn't do it this way you might get the following:
Game ships on the 26th
Early access ends on the 27th
You're locked out of the game until your package arrives on the 28th