How much time neil armstrong spent on moon?

Eagle touched down in Mare Tranquilitatis on 20 July 1969 at 20:17:40 UT (4:17:40 p.m. EDT), about 102 hours and 45 minutes into the mission. The ascent stage lifted off the next day at 17:54:01 UT, after 21 hours and 36 minutes on the lunar surface. That is the honest answer to the question: Armstrong's stay on the Moon lasted a little under a day, and most of it was spent inside a pressurised cabin roughly the size of a small lift, eating, running checks and trying to rest in a cold, noisy machine standing on four legs.

The moonwalk was a small slice of the stay. Armstrong stepped onto the surface about 109 hours and 42 minutes after launch; the extravehicular phase lasted more than two and a half hours and ended at 111 hours and 39 minutes of mission elapsed time. In that window the two men deployed the EASEP instrument package, planted the flag, took the photographs that defined the decade, spoke to the US president and collected 21.55 kg of rock and soil. Aldrin came down the ladder some minutes after Armstrong, so his own time outside was shorter still.

Caution set the schedule. Nobody knew how the suits, the cooling system or the abrasive lunar dust would behave over long exposure, so the flight plan bought only the time needed to prove that a crew could land, work and leave. Backpack consumables, the thermal environment and an ascent engine with exactly one chance to fire all argued for brevity. Later crews pushed much further, staying days rather than hours and driving a rover away from the lander. Measured against them, Armstrong's 21 hours and 36 minutes read like a rehearsal — which is precisely what the mission was designed to be, a demonstration that the whole sequence worked at all.