Apollo 8, Launched on December 21, 1968, was the first manned mission to leave Earth orbit and head for the moon. After ten lunar orbits it was time to go home. To get back on the right path, the crew had to perform the Trans-Earth Injection burn while on the far side and out of radio contact with NASA. Everything went as planned, and when radio contact was restored (at the precise time calculated by NASA engineers) this was the transmission:
Apollo 8: Houston, Apollo 8. Over.
Mission Control: Hello, Apollo 8. Loud and clear.
Apollo 8: Please be informed there is a Santa Claus.
Mission Control: That's affirmative. You're the best ones to know.
It was December 25.
If NASA’s authority isn’t enough to convince you, take a look at NORAD’s (North American Aerospace Defense Command) Santa Tracker website. They’ve been tracking the jolly old elf since 1955 using state of the art radar equipment.