Constant chrono::datetime::UNIX_EPOCH_DAY

const UNIX_EPOCH_DAY: i64 = 719_163;

Number of days between Januari 1, 1970 and December 31, 1 BCE which we define to be day 0. 4 full leap year cycles until December 31, 1600 4 * 146097 = 584388 1 day until January 1, 1601 1 369 years until Januari 1, 1970 369 * 365 = 134685 of which floor(369 / 4) are leap years floor(369 / 4) = 92 except for 1700, 1800 and 1900 -3 + –––– 719163