Here:
http://franchise.civilization.com/en/news/2016-06-civilization-vi-envoys-and-city-states/
you can SSs on which it can be read:
turn 33. 2720 BC
turn 53: 920 BC
So we can make guesses on game length...
My first thoughts:
Game can begin in 6000BC
my guess:
turns 1-20: 110 yrs leaps, 6000BC to 3910BC
turns 20-53: 90 yrs leaps, 3910BC to 920BC
maybe turns 20-60 with 90 yrs leaps...? turn 60: 290BC
(will be edited)
http://franchise.civilization.com/en/news/2016-06-civilization-vi-envoys-and-city-states/
you can SSs on which it can be read:
turn 33. 2720 BC
turn 53: 920 BC
So we can make guesses on game length...

My first thoughts:
Game can begin in 6000BC
my guess:
turns 1-20: 110 yrs leaps, 6000BC to 3910BC
turns 20-53: 90 yrs leaps, 3910BC to 920BC
maybe turns 20-60 with 90 yrs leaps...? turn 60: 290BC
(will be edited)