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The Hitman website has a handy release schedule for when the first bit of content will be out tomorrow for the latest in the franchise. Their schedule includes all platforms and various timezones so you can prepare yourself for some marathon gaming sessions.
PS4
If you're in SCEE regions (Europe, Middle East, Africa and Oceania), the game will have a rolling midnight launch, meaning that when it's 00:01 on March 11th in your country, the game will be available.

For SCEA regions, (United States, Canada and Latin America), the game will unlock for everybody at one time: March 11, 00:01 PST

Xbox One
HITMAN will have a rolling midnight launch, so when the clock hits 00:01 on March 11 in your country, the game will be available - with one exception.
In the US, all players will get access at the same time: March 11, 00:01 EST

PC via Steam
All PC players will get access to the game at the same time globally, starting on 09:01 PST, March 11.

Platform Launch Style Australia UK West Coast US
PS4 SCEE Rolling Midnight Local 00:01 11th March AEDT 00:01 11th March GMT N/A
PS4 SCEA Single Regional N/A N/A 00:01 11th March PST
Xbox One Rolling Midnight Local
(except US)
00:01 11th March AEDT 00:01 11th March GMT 00:01 11th March EST
PC Single Global 04:01 12th March AEDT 17:01 11th March GMT 09:01 11th March PST