The official site has today cleared up a few questions and confirmed what we’ve been told elsewhere – the demo will be available to download on the 20th, and it’ll be out at about noon Tokyo time.
So, that’s 3 in the morning (Friday night/Saturday morning) for GMT, 11 at night (Friday night) for East Coast Americans, and 8 at night (Friday night) for West Coast Americans.
The site also says that the demo will include GT TV and the news feeds, plus online 16-player racing, but all these features will be removed once Prologue is released.