Autumnal Equinox – Fall Equinox
Equinoxes are opposite on either side of the equator, so the autumnal (fall) equinox in the Northern Hemisphere is the spring (vernal) equinox in the Southern Hemisphere and vice versa.
Not Entirely Equal Day & Night
On the two equinoxes every year the Sun shines directly on the Equator and the length of day and night is nearly equal – but not exactly.
The September equinox marks the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator – from north to south and vice versa in March.
Autumnal Equinox – Northern Hemisphere
(USA, Central America, Canada, Europe, Asia, northern Africa)
September Equinox in Washington DC, District of Columbia, USA is on
Friday, September 22, 2017 at 4:02 pm EDT (Change city)
September Equinox in Universal Coordinated Time is on
Friday, September 22, 2017 at 20:02 UTC
First Day of Fall?
In the Northern Hemisphere, the fall equinox marks the first day of fall (autumn) in what we call astronomical seasons. There's also another, more common definition of when the seasons start, namely meteorological definitions, which are based on average temperatures rather that astronomical events.
Autumnal Equinox – Southern Hemisphere
(Australia, New Zealand, South America, southern Africa)
March Equinox in Washington DC, District of Columbia, USA is on
Tuesday, March 20, 2018 at 12:15 pm EDT (Change city)
March Equinox in Universal Coordinated Time is on
Tuesday, March 20, 2018 at 16:15 UTC
Vernal & Autumnal Equinox
- Vernal (Spring) Equinox
- Autumnal (Fall) Equinox
- March Equinox
- 10 Facts: March Equinox
- March Equinox Celebrations
- September Equinox
- 10 Facts: September Equinox
- September Equinox Celebrations
- Nearly Equal Night & Day
The Science of Seasons
- What Causes Seasons?
- Earth's Axis Is Tilted
- Meteorological vs. Astronomical Seasons
- What Is a Solar Analemma?
Winter & Summer Solstices
- What Is the June Solstice?
- June Solstice Facts
- What Is the December Solstice?
- December Solstice Facts
- When Is the Summer Solstice?
- When Is the Winter Solstice?
- June Solstice Celebrations
- December Solstice Celebrations