On December 25th:
Celebrate Merry Newton Day
Isaac Newton (12/25/1642 — 3/20/1726)
“If I have seen further than other men, it is because I have stood on the shoulders of giants.” — Isaac Newton
His birthday could be a reason for the season, apart from the solstice, so what better time to celebrate the greatest scientist who ever lived?
English physicist, mathematician and a key figure in the scientific revolution. The best minds of the Royal Society were trying to find a mechanical explanation for planetary motion. They were stumped.
In desperation, Halley (of comet fame) remembered some guy, Newton, who had seemed pretty smart. He went to visit him in Cambridge to see if he had any ideas for helping solve the problem. Newton, perhaps bored, mentioned he had solved that problem some time ago, and he'd see if he could find his proof.
He couldn't find his notes so he wrote Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), published, with help from Halley, in 1687. His book laid the foundations for classical mechanics, and to help clarify he independently invented calculus. Newton made seminal contributions to optics, the laws of motion and universal gravitation, which dominated scientists' view of the physical universe for the next three centuries.
When Einstein made his contributions, he was standing on the shoulders of Newton.
As for Newton's oddities, well, as Steven Weinberg noted, "it takes religion."