When does the first day of fall occur?

The first day of fall or the Autumn Equinox marks the start of fall in the Northern Hemisphere and also the start of spring in the Southern hemisphere. This day falls either between the 22nd and 23rd of September every year. The first-day fall is marked by what is known as ‘Autumnal Equinox.’ The first day of fall in 2018 will fall on the 22nd of September at 9:54 pm (Eastern Time ET).

Equinox is a moment where both the hemispheres, northern and southern, receive equal sun time and experience almost same day and night hours.

Since thousands of years ago, many ancient buildings such as the Stonehenge and El Castillo were built to observe the Equinoxes. During the equinoxes, these buildings show unusual sights to the human eye.

The first day of autumn also marks the beginning of winter in the Northern Hemisphere. Beautiful colors of red, orange and yellow can be seen all through the Northern Hemisphere, and low temperatures are also experienced with days facing a below 70-degree Fahrenheit.

When is the first day of fall 2017, 2018, 2019, 2020?

The following are the date and time when the First Day of fall has been observed and will be in the coming years:

  • 2017 – 22nd September, Friday
  • 2018 – 22nd September, Saturday at 9:54 pm ET
  • 2019 – 23rd September, Monday
  • 2020 – 22nd September, Tuesday

What is an Equinox?

Equinox is that day when the sunlight falls precisely perpendicular to the earth’s celestial equator. This enables the sun rays to fall equally in the southern and northern hemispheres.

Below pictures beautifully depicts the change of seasons by four different positions of earth on the elliptical orbit. These four positions are –

Equinox Explanation with representation

Autumnal Equinox

During the Equinoxes, the length of day and night are almost equal. The Sun moves from the North toward the South crossing the celestial Equator on its way, and both the Southern and Northern Hemispheres receive equal sunlight.

How do you accurately determine when the fall is close?

While the Southern Hemisphere countries such as Australia, New Zealand, and many others experience what the Northern Hemisphere does in March, the Northern hemisphere experiences something different around the first day of fall. The following are the signs that the first day of fall is near:

  1. Leaves begin to fall off trees like crazy and pile up everywhere
  2. The color of Autumn which is Red, Yellow and Orange slowly starts to spread and are noticed everywhere
  3. Flowers such as Chrysanthemums bloom beautifully, and pumpkins and maize also see good growth
  4. During the fall season, while the days are short, the nights are long
  5. The sun’s arc starts shifting toward the South
  6. The birds and butterflies just like the Spring Equinox start moving in the path of the sun toward the south

Meteorological vs. Astronomical

  • The meteorological theory depends on the seasons and temperatures, and according to them the first day of fall begins on the 1st of September in 2018
  • The cosmological approach takes into account the position of the Earth about the sun. According to the this the first day of fall is observed on the 23rd of September in 2018

Ancient buildings that mark both the autumn and Spring Equinox

  1. The Stonehenge: People from all over the world visit the Stonehenge in Britain every year to see the Sun alighting perfectly with the ancient rocks during the first day of fall. It is one of Britain’s most famous Heritage site and is opened at dawn so all can experience that beauty of nature.
  2. El Castillo in Chichen Itza: Built during 1000 AD in the ruins of Mayan which is currently in Mexico, the El Castillo was built as an ode to the serpent God named Kukulkan. During the equinoxes’ sunset, the light hits a perfect angle, making a shadow on the stairs of the building of a snake.
  3. Machu Picchu at Peru: Peru’s beautiful Machu Pichu built in the mountains is very hard to be seen by the eye from below. But at midday on the day of both the equinoxes, the sun hits the holy Intihuatana Stone directly and does not produce any shadow and can be visible very easily.

Some other famous buildings are Mnajdra in Malta, The Great Pyramid of Giza Angkor Wat in Cambodia and Tikal in Guatemala.

When is the last day of fall observed?

Just like the first day of fall, the date of the last day of fall is also split due to the two different cycles that prevail.

  1. According to the meteorological cycle, the last day of fall in 2018 will be observed at the end of November
  2. According to the astronomical cycle, the last day of fall will be observed toward the end of December in 2018

Facts about the Autumn Equinox

  1. Autumn Equinox is the perfect time to witness the Aurora borealis displays. Aurora Displays are a kind of light show in the sky as colors of red and green splashes across the sky
  2. Everyone on earth no matter where will experience sunrise in the exact east and sunset in the west
  3. Almost equal Day and night is experienced
  4. As days during this time shortens animals living in high altitudes face a lot of changes biologically