Autumn Equinox 2021: A September Date Key To Change Of Seasons Worldwide

Autumn Equinox 2021: An equinox occurs twice a year — once in spring and once in autumn — when the Sun appears directly above the Equator and we get a day and night of almost equal length

Representational image (Source: Getty)

New Delhi: Earth is slightly tilted on its axis, because of which different parts of it get unequal amounts of sunlight during different times of the year as the planet travels around the yellow star. 

What would have happened if our Earth were not tilted like this?

There would be no seasons. The Sun would always remain exactly above the Equator, and every location would receive a fixed amount of sunlight. 

These are, however, days when the Sun does appear directly above the Equator. And when this happens, we get a day and night of almost equal length — i.e. around 12 hours each. This astronomical event is known as an equinox — a mix of two Latin words: aequus (equal) and nox (night).

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 Responsible for the change of seasons on Earth, an equinox occus twice a year — once in spring and once in autumn.

In the northern hemisphere, the spring equinox occurs in March (March 20 or 21) and the autumn equinox happens in September (September 22 or 23). 

The seasons are reversed in the southern hemisphere. When it's spring equinox in the northern hemisphere, the date marks the autumn equinox in the southern hemisphere, and vice versa.

We proceed towards winter after the autumn equinox as days begin to get shorter and the nights longer. 

When Is Autumn Equinox 2021 In India?

India is part of the northern hemisphere and will mark the autumn equinox this year on Thursday, September 23.

The equinox sunrise is likely at 06:09 am and the sunset at 06:16 pm, and the day length will be 12 hours, 06 minutes and 34 seconds.

Days will begin to get shorter after Thursday. For example, the day length on Friday, September 24 will be 12 hours, 04 minutes and 52 seconds. 

About 67.3 per cent of the Earth’s landmass is situated in the northern hemisphere, which includes the entire North America, Central America, and Europe, besides the northern part of South America, major parts of mainland Asia and about two-thirds of northern Africa.

The northern hemisphere experiences summer from June to September and winter from December to March.

Equinox Celebration Across The World 

The September equinox is celebrated in different ways across the world.

The full moon around the autumnal equinox is celebrated as Harvest Moon, which is considered to be the year’s brightest and biggest full moon.

The festive season begins with the Harvest Moon.

In India, this full moon is known as the Bhadrapada Purnima, which will be observed on September 20. The day marks the beginning of Pitripaksha, the fortnight when the ancestors are remembered and worshipped.

In many countries in the northern hemisphere, the Harvest Moon coincides with the fall harvest season and sees traditional celebrations. 

China has for ages celebrated Zhongqiu Jie, or the Mid-Autumn Festival, also called the Moon Festival, around this time. The Koreas celebrate a similar festival, Chuseok.

In Europe, people greet the September equinox with song and music. London usually sees people meet up on Primrose Hill to usher in the new season.

The Chumash, a Native American tribe in Southern California, celebrate Hutash, while Japan observes the equinox day as Higan, which is a public holiday.