The Phases of the Moon
It's Chinese New Year. Be sure to eat your black-eyed bamboo shoots.
Chinese New Year is based on the Lunar Calendar. The most populous nation on earth can't help but keep track of irregular monthly cycles.
Beethoven's Moonlight Sonata was written during a Waxing Gibbous moon. Mrs. Gibbous later moved to Brazil where her scandalous grooming procedures slanted the other way.