Call of Duty has been described as the gold standard of first-person shooter video games. Their early focus on World War II notwithstanding, the games have evolved into a cultural touchstone in their more modern incarnations. So it's no surprise to learn that every year, Call of Duty players collectively log some 475,000 years of gameplay. Add it up, and over the course of their six-year history, Activision's 21st-century-themed combat simulations have cost us 2.85 million man-years — more than 14 times longer than humanity has existed.