My first Common Lisp programming job was for Mercury Scheduling (no longer around) working on the back end of airline crew control software. The main focus was assisting crew controllers in scheduling personnel on flights. We had to satisfy literally hundreds of constraints from union regulations, government regulations to…what else?…oh yeah, the constraints of reality like not being in two places at once or starting a new shift 1000 miles away in an hour’s time (computers are stupid, you have to tell them everything!).
One thing I learned is just how complicated time can be when you are inside a computer! Timezones, daylight savings, leap years, leap centuries, leap seconds….it’s a real mess.
Well, it turns out that leap years, or more generally the difference between the calendar and the actual orbit of the earth around the sun, cause a discernible albeit insignificant effect in the monthly temperature anomalies. The actual orbitally controlled seasons are not in sync with the conventional calendar.