Vernal equinox
The vernal equinox (or spring equinox) marks the beginning of astronomical spring. It occurs during the month of March in the Northern Hemisphere, and during September in the Southern Hemisphere. In Chinese culture the vernal equinox marks the middle of spring. At the same moment that the vernal equinox occurs in one hemisphere, it is the time of the autumnal equinox in the other hemisphere.
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Astronomy
The Celestial Equator and the Ecliptic are two Great Circles. As such, they intersect at two points, the Equinoxes. When the Sun, which moves along the Ecliptic, occupies the point that crosses the Equator while heading north, it is the time of the Vernal Equinox.
Due to the Precession of the Equinoxes, the point of intersection moves completely around the sky in a 25,800-year cycle. This century it is in the southwest portion of Pisces moving slowly toward Aquarius.
Chunfen in Chinese calendar
Chunfen (春分) is a solar term begins when Sun lies between the celestial longitude of 0° and 15°. It sometimes refers in particular to the day when Sun exactly at the celestial longitude of 0°. It usually begins around March 21, and ends around April 5.
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Holidays
The Iranian festival of Norouz is celebrated on the vernal equinox, as are the Bahá'í Naw-Rúz (which marks the beginning a new year in the Bahá'í calendar), and the Wiccan Sabbat of Ostara (or Eostar).
In Japan, Vernal Equinox Day (春分の日 Shunbun no Hi) is an official national holiday, and is spent visiting family graves and holding family reunions.
Easter is celebrated on the Sunday after the first ecclesiastical full moon day on or after the ecclesiastical vernal equinox day 21 March (see computus).
Earth Day was initially celebrated on the vernal equinox, 21 March 1970. It is currently celebrated in America on 22 April.
Tamil and Bengali New Years are celebrated after the sidereal vernal equinox (14 April). The former is celebrated in the South-Indian state of Tamil Nadu, and the later in Bangladesh and the East-Indian state of West Bengal.
Egg-balancing myth
A common old wives' tale regarding the vernal equinox is that this is the one day of the year that eggs can be balanced on their end. Although this myth is untrue (eggs can be balanced on any date with enough patience) and unsound (would it be different in both hemispheres? Why only the instant of vernal equinox? Why not autumnal equinox?) it is often perpetuated in the news. For a fuller treatment of the issue, see Snopes.com or BadAstronomy.com.
This myth was also featured on "The West Wing" in the episode titled "Evidence of Things not Seen" (s4e20).
