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Autumnal Equinox

Last updated date: 25th Feb 2024
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What is Equinox?

An Equinox is an astronomical phenomenon that occurs twice a year, once in the spring and once in the fall, when the Earth's axis is turned neither away from nor towards the Sun. The inclination of the Earth (with respect to the Sun) is 0° at Equinoxes, and the day and night are almost equal in length on Equinox day, i.e. 12 hours. 

Equinoxes occur every year on the 20th or 21st of March and the 22nd or 23rd of September, and all days have the same duration of day and night. In the Northern Hemisphere, March Equinox is known as Vernal Equinox and Spring Equinox, while it is known as Autumnal Equinox and Fall Equinox in the Southern Hemisphere. In other words, it is springtime in the United Kingdom, the United States, Canada, Russia, India, and China on March Equinox, while it is autumn in Australia, Argentina, Chile, New Zealand, and South Africa.

Equinoxes are preferably referred to as March Equinox (Northern Equinox) and September Equinox (Southern Equinox).  

This only occurs twice a year, on the spring and autumn equinoxes. This means that on these days, the day period is the same (12 hours) at all points on the earth's surface (except right at each pole, where it will be about to change from permanent light to dark, or vice versa). In several parts of the world, especially in the northern hemisphere, the autumnal equinox marks the start of autumn. This is the first day of spring in the southern hemisphere.

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Types of Equinoxes

Equinoxes are classified into two groups. The equinoxes in March and September are each assigned their own names.

Spring Equinox

The Spring Equinox is the first day of spring. The Spring Equinox happens as the sun reaches the equator from the southern to the northern hemisphere, marking the start of the spring season. The North Pole continues to lean back against the sun. The day and night are nearly similar in time. Spring Equinox is near 20 March.

Autumn Equinox

The Autumn Equinox occurs as the sun reaches the equator from the northern to the southern hemisphere, marking the beginning of the autumn season. The North Pole tilts away from the sun. The day and night are nearly similar in time. The autumnal equinox is near September 22nd.

Equinox and Culture

For thousands of years, equinoxes have been a part of many cultures and rituals. Equinoxes, for example, signifies the start of important days such as the new year. Planting and harvesting seasons are determined by the equinoxes. Both equinoxes are designated as national holidays in Japan as a day to honor ancestors. During the equinox, the Hindu temple Angkor Wat in Cambodia is said to be constructed in such a way that the sun rises directly above its central temple. Between 1113 and 1150, the temple was founded. There are many examples of this in various religious and cultural cultures.

Fun Facts

  • Equinoxes do not always occur on the same day each year.

  • Saturn has equinoxes as well, but they only happen every 15 years because it takes about 30 years for Saturn to orbit the Sun.

  • Equinoxes generally occur about 6 hours later each year, with a jump of a day (backward) on leap years.

  • The Mid-Autumn Festival, also known as the Moon Festival, is held in China to mark the autumnal equinox.

FAQs on Autumnal Equinox

1. Why Do the Equinoxes Not Always Occur on the Same Day Each Year?

Ans: The explanation for this is due to the time it takes the Earth to orbit the Sun and our calendar. Our year is 365 days since the Earth takes nearly 365.25 days to orbit the Sun. Every four years, we have a leap year, in which an additional day is added to our calendar to make up for the four quarters that are absent. It is important to do so in order to prevent the slow drift of the date as the seasons pass. The equinoxes do not fall at the same time every year for the same reason. 

2. What are the Dates for the Equinox for the Last Couple of Years?


Vernal Equinox (Spring) 20 March 2013

Autumnal Equinox (Autumn) 22 September 2013

Vernal Equinox (Spring) 20 March 2014

Autumnal Equinox (Autumn) 23 September 2014

Vernal Equinox (Spring) 20 March 2015

Autumnal Equinox (Autumn) 23 September 2015

Vernal Equinox (Spring) 20 March 2016

Autumnal Equinox (Autumn) 22 September 2016

Vernal Equinox (Spring) 20 March 2017

Autumnal Equinox (Autumn) 22 September 2017