When Does "Metal Gear Solid V: The Phantom Pain" (2015) Take Place?
"Metal Gear Solid V: The Phantom Pain" is a spy video game written by Hideo Kojima with Shuyo Murata, Hidenari Inamura, and Etsu Tamari designed for the PlayStation 3 and PlayStation 4 systems, that released September 1st, 2015.
It takes place on the fictional Metal Gear timeline in the year:
We know this because very early in the first level of the game, a character clearly states 9 years have passed since the events of the previous game, "Metal Gear Solid V: Ground Zeroes" (2014).

1984 AD
We know this because very early in the first level of the game, a character clearly states 9 years have passed since the events of the previous game, "Metal Gear Solid V: Ground Zeroes" (2014).
1975 + 9 = 1984.