Autumnal Equinox

An equinox is an astronomical event that occurs twice each year — once in spring and once in autumn — when the Earth’s axis is tilted neither toward nor away from the Sun. On an equinox, the Earth’s tilt relative to the Sun is effectively 0°, which means day and night are of nearly equal length — about 12 hours each.

Equinoxes fall on either the 20th or 21st of March, and either the 22nd or 23rd of September, each year, with both days having roughly equal daylight and darkness.

In March, it is spring in the Northern Hemisphere, so the March equinox is called the Vernal Equinox or Spring Equinox there. At the same time, it is autumn in the Southern Hemisphere, where the March equinox is called the Autumnal Equinox or Fall Equinox. In other words, on the March equinox, it is spring in the UK, the USA, Canada, Russia, India, and China, while it is autumn in Australia, Argentina, Chile, New Zealand, and South Africa.

Similarly, in September, it is autumn in the Northern Hemisphere, so the September equinox is called the Autumnal or Fall Equinox there — while it is spring in the Southern Hemisphere, where it is called the Vernal or Spring Equinox. So on the September equinox, it is autumn in the UK, the USA, Canada, Russia, India, and China, while it is spring in Australia, Argentina, Chile, New Zealand, and South Africa.

To avoid this confusion, equinoxes are more precisely referred to as the March Equinox (Northern Equinox) and the September Equinox (Southern Equinox).

In Hindu astrology, the Autumnal Equinox is known as Sharad Vishuva or Sharad Sampat. However, due to the precession of the equinoxes, its Hindu equivalent has gradually drifted from the astronomical date and is now instead celebrated as Tula Sankranti.