..although that depends on which calendar you're using:
Some years ago, the evolutionist and atheist Richard Dawkins pointed out to me that Sir Isaac Newton, the founder of modern physics and mathematics, and arguably the greatest scientist of all time, was born on Christmas Day, and that therefore Newton’s Birthday could be an alternative, if somewhat nerdy, excuse for a winter holiday.
All very jolly — but then, ’tis the season. Yet things are not so
simple. It turns out that the date of Newton’s birthday is a little
contentious. Newton was born in England on Christmas Day 1642 according
to the Julian calendar — the calendar in use in England at the time.
But by the 1640s, much of the rest of Europe was using the Gregorian
calendar (the one in general use today); according to this calendar,
Newton was born on Jan. 4, 1643.