The Walking Dead DLC, 400 Days, with be with us very soon, though how soon depends on where you live and what format you own.
The dates were confirmed by Telltale to IGN earlier today, and they read as follows:
Tuesday, July 2 - PSN (North America)
Wednesday, July 3 - PC/Mac (Steam, Telltale Games Store)
Friday, July 5 - XBLA (Worldwide)
Wednesday, July 10 - PSN (Europe)
Thursday, July 11 - iOS (Worldwide)