Maybe they did that on purpose that year. Maybe they were all freaked out like some were on December 31, 1999. It makes you wonder.
No, it’s the rules. Because the mismatch in our flight around the sun is odd. So leap years are:
Every year divisible by 4
Except years divisible by 100
Except except years divisible by 400
So 1900 wasn’t a leap year. 2000 was. 2100 won’t be. 2400 will be.