September 2017 is the 47th month of the Xbox One being on sale. In the latest month the gap grew in favor of the Xbox 360 by 259,825 units and by 3.25 million in the last 12 months. The Xbox 360 currently leads by 1.15 million.
Both consoles launched in November. The Xbox 360 launched in November 2005, while the Xbox One launched in November 2013. The Xbox One has sold 31.18 million units, while its predecessor the Xbox 360 sold 32.32 million units.