Almanac · Seasons

September equinox 2027

The September equinox is on Thu 23 Sep 2027 at 06:01 UTC: the instant the Sun crosses the sky’s equator heading south, overhead at noon at the equator. It begins astronomical autumn in the northern hemisphere and spring in the southern.

• Equinox Thu 23 Sep 2027, 06:01 UTC
• Sun overhead at noon The equator The Sun’s declination then: −0.00°
• Daylight 12 h 12 min at 60°N 12 h 06 min at 0°

The day at each latitude

Sunrise and sunset on Thu 23 Sep 2027 at each latitude, how long the Sun is up, which way to face to see it rise and set, and how high it climbs at noon. Times are local solar time: your clock may differ by up to an hour or two, by your time zone.

How we worked it out: the equinox is the instant the Sun’s apparent longitude reaches 180°, found to the second from the Earth’s place in VSOP87, carried to the equinox of date and given nutation and aberration, as Meeus works these instants out; the tests hold it to the U.S. Naval Observatory’s time within the minute. Sunrise and sunset are the Sun’s upper edge on a level horizon, with refraction, as /tonight gives them, at Greenwich’s longitude, and the bearings are measured from due east and due west.

• J. Meeus, Astronomical Algorithms, ch. 27: the instants of the equinoxes and solstices, from the Sun’s apparent longitude
• P. Bretagnon and G. Francou, VSOP87: the Earth’s place, which the Sun’s is the reverse of, as the planets are seen from it
• U.S. Naval Observatory, Earth’s Seasons: the instants the tests hold these to, within the minute
• J. Meeus, Astronomical Algorithms, ch. 15 and 25: sunrise and sunset, as /tonight gives them

All equinoxes and solstices · September equinox 2025 · September equinox 2026 · Why we have seasons · The year’s sky almanac · Tonight