How old was Neil Armstrong when he walked on the Moon?

Neil Alden Armstrong was born on August 5, 1930, in Wapakoneta, a small town in western Ohio, and was 38 years old on the day he stepped off the lunar module. That age says a lot about how the Apollo program worked: the generation that flew to the Moon had trained as military and test pilots in the 1950s, and reached command positions in their early thirties, in an agency that had barely existed for a decade. Armstrong was also an aeronautical engineer, a background that mattered as much as flight hours when it came to manually piloting the final meters of the descent.

There's a minor trap in the question, and it's the time. The lunar module Eagle touched down on July 20, 1969, at 20:17:40 UT, but Armstrong didn't set foot on the regolith until 02:56:15 UT on July 21. On the US East Coast it was still the night of the 20th, which is why that is the date that stuck in collective memory and on commemorative plaques. Edwin Aldrin stepped down nineteen minutes later, and the moonwalk ended at 05:11:13 UT, when the hatch was closed.

From that first step came the phrase Armstrong spoke on touching the ground: that's one small step for man, one giant leap for mankind. The rest was methodical work. The crew spent a total of 21 hours and 36 minutes on the surface, deployed instruments and collected 21.55 kg of lunar rock and soil, the first material from another body in the solar system brought to Earth by human beings. Half a century later, those samples remain the reference against which almost everything we know about lunar geology is calibrated.