What is the autumnal equinox? When is the autumnal equinox, what date does the autumnal equinox fall on and when does summer end?
The autumnal equinox occurs in September each year, and in the northern hemisphere the date marks the end of summer and beginning of autumn.
The Earth is tilted on its axis. This means that the Sun illuminates the northern or southern hemisphere more depending on where the Earth is along its orbit.
However, at two points in the year the Sun will illuminate the northern and southern hemispheres equally. These are known as the equinoxes.
When is the autumnal equinox in 2026?
In 2026 the autumnal equinox will occur on 23 September at 1.06am BST.
At two points in the year the Sun will illuminate the northern and southern hemispheres equally. These are known as the equinoxes: the autumnal equinox and vernal or spring equinox.
Creative Commons - Earth lighting equinox
Creative Commons - Earth lighting equinox
It’s the moment at which the plane of Earth's equator passes through the centre of the Sun's disk, or the moment that the Sun passes the celestial equator. On these dates, there are approximately equal hours of daylight and darkness.
The Theory of the Seasons and Signs of the Zodiac
The ecliptic: the plane in which the Earth and most of the other planets orbit around the Sun over a year
The celestial equator: an imaginary projection of the Earth's equator onto the sky
Where does the word 'equinox' come from?
The word equinox comes from the Latin aequinoctium meaning 'equal night'.
Why don't the solstices and equinoxes happen on the same days every year?
The Earth takes approximately 365¼ days to go around the Sun. This is why we have a leap year every four years to add another day to our calendar.
For the same reason the precise time of the equinoxes are not the same each year. Generally they will occur about six hours later each year, with a jump of a day (backwards) on leap years.
The Earth is tilted on its axis. This means that the Sun illuminates the northern or southern hemisphere more depending on where the Earth is along its orbit.
However, at two points in the year the Sun will illuminate the northern and southern hemispheres equally. These are known as the equinoxes.
When is the autumnal equinox in 2026?
In 2026 the autumnal equinox will occur on 23 September at 1.06am BST.
At two points in the year the Sun will illuminate the northern and southern hemispheres equally. These are known as the equinoxes: the autumnal equinox and vernal or spring equinox.
Creative Commons - Earth lighting equinox
Creative Commons - Earth lighting equinox
It’s the moment at which the plane of Earth's equator passes through the centre of the Sun's disk, or the moment that the Sun passes the celestial equator. On these dates, there are approximately equal hours of daylight and darkness.
The Theory of the Seasons and Signs of the Zodiac
The ecliptic: the plane in which the Earth and most of the other planets orbit around the Sun over a year
The celestial equator: an imaginary projection of the Earth's equator onto the sky
Where does the word 'equinox' come from?
The word equinox comes from the Latin aequinoctium meaning 'equal night'.
Why don't the solstices and equinoxes happen on the same days every year?
The Earth takes approximately 365¼ days to go around the Sun. This is why we have a leap year every four years to add another day to our calendar.
For the same reason the precise time of the equinoxes are not the same each year. Generally they will occur about six hours later each year, with a jump of a day (backwards) on leap years.
31-35, F
