Every year at the end of September, many people celebrate the Autumn Equinox, which is important not only for astronomers, but also for many people living in countries where the equinox days are celebrated as holidays.
The autumn equinox itself is an astronomical phenomenon associated with the Sun crossing the celestial equator. The line of light partition of the planet into parts illuminated and not illuminated by the Sun, called a terminator in astronomy, passes at the moment of the equinox through the Earth's poles and is perpendicular to the Earth's equator. However, this can only be seen from space.
The date of the autumn equinox in universal time falls on September 22 or 23 with the transition of the Sun from the Northern to the Southern Hemisphere. It is worth noting that south of the equator this equinox is spring, while the spring equinox in the Southern Hemisphere, celebrated on March 20 in the Northern Hemisphere, is autumn.
The generally accepted idea that the equinox is characterized by equal day and night is only partly true, since in fact the day, due to a number of factors, lasts a little longer.
A tropical year, the duration of which is determined by the period of time between two equinoxes of the same name, in Julian and Gregorian chronology does not have an exact match with calendar dates. As a result, the equinox in these calendars diverges by date and shifts. The Gregorian calendar, at the same time, is structured in such a way that the dates of the equinoxes fall on almost the same numbers, however, in this calendar, in the long term, the exact time of the equinox and even its calendar date can shift both forward and backward (spring – from March 19 to 21, and autumn – from September 22 to 24).
In pre-Christian times, in the traditions of the pagan period, all phenomena associated with the Sun acquired a sacred character. This also applied to the equinox days: both spring and autumn.
In some countries, the equinox days are public holidays (Japan), and in a number of other countries, the vernal equinox is celebrated as the beginning of a new year in addition to the generally accepted celebration of January 1.
The Day of the Autumn Equinox was also widely celebrated by the Eastern Slavs, whose pagan beliefs associated this date, among other things, with the collection of plants for amulets and forecasts for the coming winter.
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