What was Apollo 11's total mission duration?

Apollo 11’s total mission duration was 8 days, 3 hours, 18 minutes, and 35 seconds.

The mission began with the Saturn V launch from Kennedy Space Center on July 16, 1969, at 13:32 UTC. It ended when the Command Module Columbia splashed down in the Pacific Ocean on July 24. The elapsed time includes the journey from Earth to the Moon, lunar orbit, the landing and surface stay, the return to lunar orbit, the trip home, and atmospheric reentry.

Apollo 11 was not simply an eight-day stay on the Moon. Armstrong and Aldrin spent more than 21 hours on the lunar surface, while Collins remained in lunar orbit. After the Lunar Module ascent stage rendezvoused with Columbia, the crew began the trans-Earth journey and safely returned to Earth three days after leaving lunar orbit.

The exact seconds matter because mission duration is measured from launch to splashdown, not from lunar landing to Earth return. Rounded descriptions often call Apollo 11 an eight-day mission, but the official elapsed time is considerably more precise.