Apollo 11 never *left* the moon. The mission landed on the moon on July 20, 1969, and departed the lunar surface on July 21, 1969.

The crew, Neil Armstrong, Buzz Aldrin, and Michael Collins, spent a total of 21 hours, 36 minutes on the lunar surface.

Perhaps you're thinking of the time Apollo 11 left lunar orbit to return to Earth? That happened on July 21, 1969, at 17:54 GMT.