The ages of the Marvel Cinematic Universe’s superheroes aren’t particularly defining personality traits, and for the most part, the core members of the Avengers have been given relatively vague birthdays. Peter Parker was fifteen when he first appeared in Captain America: Civil War, but the franchise has never tended to settle on specifics.
For instance, Chris Hemsworth’s Thor revealed in Infinity War that he’d been around for 1500 years, while Steve Rogers joked in The Winter Soldier that he was 95 but not dead, which would make him over 100 years old by the time that Avengers: Endgame rolled around. But audiences have always just assumed that the mortal members of Earth’s Mightiest Heroes are roughly the same age as the actors who play them.
As for Tony Stark, given that he was a heightened extension of Robert Downey Jr.’s real-life personality, it seems fitting that the actor and the genius billionaire playboy philanthropist who defined his career were almost the same age. When Howard Stark reveals his wife is pregnant during Endgame‘s time heist, it confirms Tony’s date of birth as May 29th, 1970 in MCU canon.
Meanwhile, the five-year time jump following Thanos’ Snap and Iron Man’s ultimate sacrifice see him killed off in 2023, meaning that Tony was either 52 or 53 years old depending on what time of year Avengers: Endgame took place. And as for Robert Downey Jr., he was born in 1965 and turned 54 just three weeks before the film hit theaters and went on to become the highest-grossing movie ever made. Meaning that the symmetry between the actor and his most beloved character was mirrored in their ages, which is a rarity in Hollywood when you tend to see people pushing 30 trying to pass themselves off as high school students.