Calendar Systems

Age in years, months, days and days lived, Korean and East Asian ages, next birthday with leap-day rules, and zodiac.

Chinese zodiac animal, element, yin/yang and Chinese New Year date for a year or a date (New Year table 1901-2100).

Weekday of any date from year 1 to 9999 (Gregorian or Julian calendar) with day of year, quarter, ISO week and ISO week-date.

Convert a Gregorian date to the Hebrew calendar (or back) with leap year, year type and major holiday dates.

Convert a Gregorian date to the Islamic tabular civil calendar (or back); a calculated approximation, not moon sighting.

Convert between Gregorian and Julian calendar dates (Old Style / New Style) with the day difference for that date.

Julian Day, modified JD and Julian Day Number for a date and UTC time (Gregorian or Julian calendar), or JD back to a date.

Is a year a leap year in the Gregorian, Julian, Hebrew, Islamic (tabular) or Persian calendar? Rule and nearby leap years.

All new moons, first quarters, full moons and last quarters in a month (UTC) with times and a blue-moon flag.

Moon phase name, age in days, approximate illumination and the previous/next new, quarter and full moon times for a date.

Convert a Gregorian date to the Persian Solar Hijri calendar (or back) using the astronomical Nowruz rule, 1901-2100.

March and September equinox and June and December solstice moments (UTC) for a year, with season lengths in days.