How long did Apollo 11 astronauts remain on the Moon's surface?

Apollo 11 astronauts remained on the Moon's surface for 21 hours and 36 minutes.

Neil Armstrong and Edwin “Buzz” Aldrin landed the lunar module Eagle in the Sea of Tranquility on July 20, 1969. They completed one lunar surface expedition, collected samples, photographed the area, deployed experiments, and planted the United States flag.

Armstrong and Aldrin spent about two and a half hours outside Eagle during their surface excursion. The rest of their stay included eating, resting, preparing for ascent, and operating equipment inside the cabin. Michael Collins remained in lunar orbit aboard the command module Columbia.

The surface-stay duration is different from the time spent outside the spacecraft. It is also different from Apollo 11's complete mission duration, which was just over eight days from launch to splashdown. These distinctions explain why several Apollo 11 time figures appear in historical summaries.