I remember fondly the leap year wars of the late 1990s. There were endless debates over whether or not 2000 would be a leap year. It was, of course.
Still, if you ever want to have a banging-your-head-in-frustration moment or three, go read old Usenet archives about the topic. It was incredible! People cited all sorts of sources. People got into heated debates about the length of the solar year. My personal favorite is the discovery that, since the 400-year-rule (years which are multiples of 400 are leap years) is the largest-scale rule, there is a 400-year cycle which has an exact multple of 7 days. As a result, the 13th of a month is more likely to be Friday than any other day of the week… and this holds true until we change the calendar!
Trivia. Gotta love it.