Equinox – When Are Day and Night Equal? Dates & Science
When is the next equinox? Learn about the spring and autumn equinox, the science behind equal day and night, and track equinox times for your city.
When day and night are really equal – New York
- On the equinox the day is already a little longer than 12 hours; the day of equal day and night comes earlier in spring and later in autumn.
- Day and night equal: March 17 – Closest to 12:00 h of daylight – a few days away from the equinox, because of refraction and the sun's disc.
- The other one: September 26
Questions and answers
- When is the next equinox in New York? The Spring Equinox is on March 20, 2027 at 16:24 local time. That day lasts 12:08 h: sunrise 06:59, sunset 19:07.
- Are day and night really equal at the equinox? Almost: refraction and the size of the sun's disc make the day a few minutes longer than 12 hours. In New York day and night are closest to equal on March 17.
- How high does the sun climb at the equinox? At noon in New York it stands 49° above the horizon – 90° minus the latitude.
What Is the Equinox?
The equinox is the astronomical moment when the sun stands directly above the equator. On this day, day and night are nearly equal in length — roughly 12 hours each. The word comes from Latin aequus (equal) and nox (night).
There are two equinoxes per year: the spring equinox around March 20 and the autumn equinox around September 22. They mark the astronomical start of spring and autumn and are the moments of fastest daylight change.
Earth's Axis Perpendicular to the Sun
At the equinox, Earth's axis is tilted neither toward nor away from the sun. The sun rises exactly in the east and sets exactly in the west — everywhere on Earth.
Nearly Exactly 12 Hours of Daylight
Due to atmospheric refraction and the size of the solar disk, the day actually lasts a few minutes longer than 12 hours. Perfect 12h:12h symmetry occurs on the so-called 'equilux' day, which falls a few days before/after the equinox.
The Sun Travels Along the Celestial Equator
At the equinox, the sun follows the celestial equator. Afterward, it moves northward (Northern Hemisphere) or southward (Southern Hemisphere) toward the solstice, bringing longer days.
Cultural Significance
The equinox has been celebrated worldwide for millennia. The Persian Nowruz (New Year) falls on the spring equinox, the Japanese Higan festival honors ancestors at both equinoxes, and at Chichén Itzá, the Kukulkán pyramid casts a serpent shadow at the equinox.
In the modern world, equinoxes mark seasonal transitions and turning points in the light cycle. After the spring equinox, days grow noticeably longer; after the autumn equinox, noticeably shorter.
Watch Sunrise and Sunset
At the equinox, the sun rises almost exactly in the east and sets in the west. Find a clear horizon and observe this special alignment.
Feel the Daylight Change
Around the equinox, day length changes fastest — up to 3–4 minutes per day. Track the shift with SunnyTracker!
Enjoy the Light Balance
Equal portions of light and darkness create a special atmosphere. Use the day for outdoor activities in balanced, pleasant light.
Celebrate Nowruz
The spring equinox is celebrated in many cultures as a new beginning. Set new goals and enjoy the returning light!
Closest to 12:00 h of daylight – a few days away from the equinox, because of refraction and the sun's disc.
They don't fall on the solstice itself – the equation of time shifts them by days or weeks.
The earliest sunset comes before the shortest day, the latest sunrise after it – the equation of time shifts them.
On the equinox the day is already a little longer than 12 hours; the day of equal day and night comes earlier in spring and later in autumn.