Autumn equinox 2023: How is the date decided and does it change every year?
THE Autumn equinox is an event that happens every year to signify the start of the season.
Despite the specific date varying each year, it tends to fall in the same month.
What is the autumn equinox?
The autumn equinox happens each September and is the official start of the season.
It occurs when there is the same amount of daylight and nighttime, which signifies the end of summer.
Through the year, the Earth is tilted on its axis and the sun illuminates the northern or southern hemisphere more depending on where the planet is in its orbit.
When the sun illuminates the northern and southern hemispheres equally, this is known as an equinox.
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When is the first official day of autumn?
The meteorological start of autumn is marked by the first day of September every year.
However, the official start of autumn is when the equinox falls.
2023's autumn equinox will land on Saturday, 23 September.
What time is the autumn equinox?
The autumn equinox will occur at 7.50am BST.
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This is when daytime will transition into night, with equal parts of both.
The word equinox comes from the Latin aequinoctium meaning equal night.
How is the autumn equinox date decided?
The autumn equinox tends to fall around September 22 or 23 each year.
The dates vary because of the difference between how the Gregorian calendar defines a year as 365 days and the time it actually takes for Earth to complete its orbit around the Sun which is about 365.25 days.
The day of the equinox can vary slightly due to the addition of an extra day every four years.
Does the autumn equinox change every year?
Yes, the date of the autumn equinox can change each year but just by a few days.
The reason is similar to why we have a leap year every four years.
The Earth takes approximately 365.25 days to go around the Sun which is why we have a leap year every four years to add another day to our calendar.
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For the same reason, the exact time of the equinoxes is not the same each year.
They tend to occur about six hours later each year, with a jump of a day on leap years.