What Time Does the Game Start?

Can anyone tell me when the game begins? The NFL and ABC say "the game" begins at 6:00, not just the "pre-game coverage" (which starts at 2:30), but the actual game--flippin' liars.

Yahoo says the game starts at 6:18.

WaPo says it starts at 6:30.

I spent nearly thirty minute searching for the exact start time, but couldn't find it. Anyone know for sure? Is this one of the greatest American secrets, along with "Who killed JFK"? If so, why?