5 services carry this tag in their source record. Tags come from the provider, not from us — a tag is a claim about what the service does, not proof that it does it well.
Convert between Unix epoch timestamps and ISO 8601 date strings in both directions. Provide either an epoch (seconds or milliseconds) or an ISO date string. Returns both representations plus UTC and date components.
Get the day number within the year (1-366) for any date, plus days remaining, leap-year status, percent of year complete, and a simple (Sunday-start) week number.
Compute the date of Easter Sunday for a given year using the Anonymous Gregorian algorithm (Meeus/Jones/Butcher). Also returns Good Friday, Ash Wednesday, Palm Sunday, Pentecost, and the day-of-year for Easter.
Get the ISO 8601 week number, ISO day-of-week, quarter, and day-of-year for any date. Useful for fiscal/reporting calendars, weekly aggregations, and sprint planning.
Check whether a year is a leap year and get related info: days in that year, the next and previous leap years, and the Gregorian leap-year rule.