National Gorilla Suit Day
It's all explained HERE.
From Today In Science History: On this date in 1961, the U.S. launched a 4-year-old male chimpanzee named Ham on a Mercury-Redstone 2 rocket into suborbital flight. During his 16.5 minute suborbital flight, Ham experienced about 7 minutes of weightlessness, reached an altitude of 108 miles and a speed of 13,000 mph. Ham was recovered safely 1,425 miles downrange.