Equinox

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An equinox is a moment of the year when the sun crosses the equator. The day and night are close to being of the same length (ca. 12 hours each). There are two equinoxes a year: The Spring equinox marks the beginning of spring and the Autumn equinox marks the beginning of Autumn (see seasons).

The dates of the Spring Equinox and Autumn Equinox depend of course on the hemisphere of Earth.

One equinox occurs on March 19, 20 or 21, which may be referred to as the March Equinox or the Northward Equinox. It is the Spring Equinox in the Northern Hemisphere and the Autumn Equinox in the Southern Hemisphere.

The other equinox occurs on September 22 or 23, which may be referred to as the September Equinox or Southward Equinox. It is the Spring Equinox in the Southern Hemisphere and the Autumn Equinox in the Northern Hemisphere.

The term Vernal Equinox may mean either the March Equinox or Spring Equinox.

see also: solstice, precession