Calendar rules, weekday and date algorithms, clock and astronomical timekeeping.
Tests whether a Gregorian year has 366 days.
Angle between the hour and minute hands of an analog clock.
Finds the day of the week for any Gregorian date.
Gauss's weekday formula — find which day of the week any birthdate fell on.
Continuous day count used by astronomers to compare dates.
Number of days separating two calendar dates.
Whole years elapsed since a birth date.
Seconds elapsed since 1970-01-01 00:00:00 UTC (the epoch).
Earth's rotation period measured against the stars, not the Sun.
ISO-8601 week of the year (weeks start on Monday).
Convert Coordinated Universal Time to a local zone.
Difference between sundial (apparent) and clock (mean) time.
A repeating event's period is the reciprocal of its frequency.
Day-of-year number (1–366) for a given date.
Core step of the Gregorian algorithm locating the Paschal full moon.