autumnal equinox
Fall's official start
The autumnal equinox is one of two moments each year when day and night are approximately equal in length, occurring around September 22 or 23 in the Northern Hemisphere.
It marks the astronomical beginning of autumn, when the sun crosses the celestial equator heading south.
The autumnal equinox signals shorter days ahead.
In the Southern Hemisphere, this same moment marks the vernal equinox and the start of spring.
- phenologyStudy of seasonal cycles
- axial tiltRotational axis deviation
- SukkotJewish autumn harvest commemoration
- celestial equatorSphere's midplane above us
- night skyDarkness above after sunset
harvest moon · natural cycles · falling leaves · changing colors · September · migratory birds · hibernation · astronomical events · fall · seasonal change · abundance · cider · sweater weather · leaves · first frost · pumpkin · pumpkin spice · apple picking
- seasonssummer, winter, spring, fall, summertime
- astronomy termseclipse, solar eclipse, lunar eclipse, star, meteor shower
- autumnleaf fall, fall, golden leaves, changing colors, pumpkins
- observancesholidays, holy days, commemorations, anniversaries, Remembrance Day
- time periodsday, year, month, week, hour
- astronomystars, moon, sun, planet, planets
autumnal equinoxvernal equinox
Spring's astronomical beginning
spring equinox · March equinox · first day of spring · Nowruz · summer solstice
autumnal equinoxsummer solstice
Longest daylight of year
winter solstice · solstice · December solstice · June solstice · midwinter