TIL Leap year

Number of days per year in the Gregorian calendar: 365 + 1⁄4 − 1⁄100 + 1⁄400 = 365 + 97⁄400 = 365.2425 days.

Tropical (solar) year: 365.24219 days.

The Gregorian calendar, with its leap year system, brings them close, but the discrepancy of 0.00031 days per year will cause a one-day drift over approximately 3226 years.