Grand Theft Auto V was released on Xbox 360 and PlayStation 3 this past Tuesday, the 17th September. In just 24 hours, it hit $800M in sales, so it should be no surprise that the game on both console platforms reached $1B just two days later.
To give an idea of just how fast this was, Call of Duty: Black Ops 2 was the previous record holder, taking 15 days to hit $1B; GTA5 beat it by a factor of 500%.