US Naval Observatory

• Get sun and moon timesGet sunrise, sunset, solar noon, dawn and dusk (civil twilight), moonrise, moonset and the Moon's phase and illumination for one day at a place, in local time.
• List upcoming moon phasesList the next new moons, first quarters, full moons and last quarters from a date, with their exact times.
• List moon phases for a yearList every new moon, first quarter, full moon and last quarter in a calendar year, with their exact times.
• Get equinoxes and solsticesGet the exact times of a year's equinoxes and solstices (the starts of the seasons) and of Earth's perihelion and aphelion (closest to and farthest from the Sun).
• List solar eclipses in a yearList the solar eclipses of a year, with their dates and kinds (total, annular, hybrid or partial).
• Get a solar eclipse at a placeSee how a solar eclipse looks from a place: whether it is visible, how much of the Sun is covered, how long it lasts, and when each stage happens with the Sun's position in the sky.
• Get sidereal timeGet the sidereal (star) time at Greenwich and at a place, mean and apparent, for a moment or a series of moments: what telescopes use to point at the sky.
• Convert date to Julian dateTurn a calendar date and time into its Julian date, the day count astronomers use. Works from 4713 BC to AD 9999; dates before 15 October 1582 are read in the Julian calendar.
• Convert Julian date to dateTurn a Julian date into its calendar date, time (UT1) and day of the week. Dates before 15 October 1582 come back in the Julian calendar.
• List Easter and Christian holy daysList the dates of Ash Wednesday, Palm Sunday, Good Friday, Easter, Ascension Day, Pentecost, Trinity Sunday and the First Sunday of Advent in a year (Western churches).
• List Jewish holy daysList the dates of Rosh Hashanah, Yom Kippur, the first day of Sukkot, Hanukkah, the first day of Passover and Shavuot that fall in a year, with each one's Hebrew calendar year. Holidays begin at sunset the evening before.
• List Islamic holy daysList the dates of the Islamic New Year and the first days of Ramadan and Shawwal that fall in a year, with each one's Islamic calendar year. These are calculated dates; local observance can differ by a day.
• Get US daylight saving time datesGet the dates US daylight saving time begins and ends in a year (1967 onwards).
• Get celestial navigation dataGet the almanac data for working out a position from sextant sights: for an assumed position and time, each body above the horizon with its declination, Greenwich hour angle, computed altitude and azimuth, and the altitude corrections.

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