Fall Equinox 2014: Time, Date, and Definition for Autumnal Equinox

September 9, 2014 Updated: July 18, 2015

The September Equinox, also known as the Autumnal or Autumn Equinox, is set to take place later this month.

The date will actually be different depending on where you are, the National Weather Service explains.

The official time is 0229 UTC time on Tuesday, September 23. But because the United States is behind Universal Time, the Autumn Equinox will actually fall on Tuesday, September 23 at 10:29 p.m. EDT (9:29 p.m. CDT, 8:29 p.m. MDT).

The equinox  “is the moment when the Sun shines directly on the Earth’s equator and equally lights up the Northern and Southern Hemispheres,” explained NASA’s Jet Propulsion Laboratory in a blog post.

“This equinox marks the beginning of Fall in the Northern Hemisphere, and Spring in the Southern Hemisphere.”

The National Weather Service says that the word equinox is derived from two Latin words – aequus (equal) and nox (night).

“At the equator, the sun is directly overhead at noon on these two equinoxes. The ‘nearly’ equal hours of day and night is due to refraction of sunlight. or a bending of the light’s rays that causes the sun to appear above the horizon when the actual position of the sun is below the horizon. Additionally, the days become a little longer at the higher latitudes (those at a distance from the equator) because it takes the sun longer to rise and set,” it said.

“Therefore, on the equinox and for several days before and after the equinox, the length of day will range from about 12 hours and six and one-half minutes at the equator, to 12 hours and 8 minutes at 30 degrees latitude, to 12 hours and 16 minutes at 60 degrees latitude.”

While those south of the equator will begin to enjoy longer days and warmer weather, people in the United States and other parts of the world will have to deal with increasingly shorter days and increasingly cold weather.


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