- The Persian new year, Nowruz, is held annually on the vernal equinox, as the beginning of spring.
- Wiccans and Neopagans celebrate the Sabbats of Ostara on the spring equinox, and Mabon on the autumnal equinox.
- The September equinox marks the first day of Mehr or Libra in the Persian calendar. It is one of the Iranian festivals called Jashne Mihragan, or the festival of sharing or love in Zoroastrianism.
- Sham El Nessim was an ancient Egyptian holiday which can be traced back as far as 2700 B.C. It is still one of the public holidays in Egypt. Sometime during Egypt's Christian period (c. 200-639) the date moved to Easter Monday, but before then it coincided with the vernal equinox.
- The Jewish Passover usually falls on the first full moon after the Northern Hemisphere vernal equinox, although occasionally (4 or 5 times every 19 years) it will occur on the second full moon.
- The Christian churches calculate Easter as the first Sunday after the first full moon on or after the March equinox. The official church definition for the equinox is March 21; however, as the Eastern Orthodox Churches use the older Julian calendar, while the Western Churches use the Gregorian calendar, both of which designate March 21 as the equinox, the actual date of Easter differs. The earliest possible Easter date in any year is therefore March 22 on each calendar.
- The March equinox marks the first day of various calendars including the Iranian calendar and the Bahá'í calendar. The Persian (Iranian) festival ofNowruz is celebrated then. According to the ancient Persian mythology Jamshid, the mythological king of Persia, ascended to the throne on this day and each year this is commemorated with festivities for two weeks. These festivities recall the story of creation and the ancient cosmology of Iranian and Persian people. It is also a holiday for Azerbaijan,Afghanistan, India, Turkey, Zanzibar, Albania, and various countries of Central Asia, as well as among the Kurds. As well as being a Zoroastrian holiday, it is also a holy day for adherents of the Bahá'í Faith and the Nizari Ismaili Muslims.
- The traditional East Asian calendars divide a year into 24 solar terms (節氣, literally "climatic segments"), and the vernal equinox (Chūnfēn, Chinese and Japanese: 春分; Korean: 춘분;Vietnamese: Xuân phân) and the autumnal equinox (Qiūfēn, Chinese and Japanese: 秋分; Korean: 추분; Vietnamese: Thu phân) mark the middle of the spring and autumn seasons, respectively. In this context, the Chinese character 分 means "(equal) division" (within a season).
- In Japan, (March) 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. Similarly, in September, there is an Autumnal Equinox Day (秋分の日 Shūbun no hi).
- The Mid-Autumn Festival is celebrated on the 15th day of the 8th lunar month, oftentimes near the autumnal equinox day, and is an official holiday in many East Asian countries. As the lunar calendar is not synchronous with the Gregorian calendar, this date could be anywhere from mid-September to early October.
- Tamil and Bengali New Years follow the Hindu zodiac and are celebrated according to the sidereal vernal equinox (April 14). The former is celebrated in the South Indian state of Tamil Nadu, and the latter in Bangladesh and the East Indian state of West Bengal.
- In many Arab countries, Mother's Day is celebrated on the March equinox.
- The harvest festival in the United Kingdom is celebrated on the Sunday of the full moon closest to the September equinox.
- Modern innovations:
- The September equinox was "New Year's Day" in the French Republican Calendar, which was in use from 1793 to 1805. The French First Republic was proclaimed and the French monarchy was abolished on September 21, 1792, making the following day (the equinox day that year) the first day of the "Republican Era" in France. The start of every year was to be determined by astronomical calculation, (that is: following the real Sun and not the mean Sun as all other calendars).
- World Storytelling Day is a global celebration of the art of oral storytelling, celebrated every year on the spring equinox in the northern hemisphere, the first day of autumn equinox in the southern.
- World Citizen Day occurs on the March equinox.
- Earth Day was initially celebrated on March 21, 1970, the equinox day. It is currently celebrated in various countries on April 22.
Myths, fables and facts
- For a Latin word like nox the plural is noctēs. Although this root is retained in English in the adjective: equinoctial — it is not commonly used for the plural, which is equinoxes, rather than equinoctes.
- One effect of equinoctial periods is the temporary disruption of communications satellites. For all geostationary satellites, there are a few days near the equinox when the sun goes directly behind the satellite relative to Earth (i.e. within the beamwidth of the groundstation antenna) for a short period each day. The Sun's immense power and broad radiation spectrum overload the Earth station's reception circuits with noise and, depending on antenna size and other factors, temporarily disrupt or degrade the circuit. The duration of those effects varies but can range from a few minutes to an hour. (For a given frequency band, a larger antenna has a narrower beamwidth, hence experiences shorter duration "Sun outage" windows).
- A modern folk-notion[clarification needed] claims that on the March equinox day (some may also include the September equinox day rather than leaving it out), one can balance an egg on its point. However, one can balance an egg on its point any day of the year...if one has enough patience.
- Although the word equinox is often understood to mean "equal [day and] night," as is noted elsewhere, this is not strictly true. For most locations on earth, there are two distinct identifiable days per year when the length of day and night are closest to being equal; those days are commonly referred to as the "equiluxes" to distinguish them from the equinoxes. Equinoxes are points in time, but equiluxes are days. By convention, equiluxes are the days where sunrise and sunset are closest to being exactly 12 hours apart. This way, you can refer to a single date as being the equilux, when in reality, it spans from sunset on one day to sunset the next, or sunrise on one to sunrise the next.
- What is true about the equinoxes is that two observers at the same distance north and south of the equator will experience nights of equal length.
- The equilux counts times when some direct sunlight could be visible, rather than all hours of usable daylight (which is any time when there is enough natural light to do outdoor activities without needing artificial light). This is due to twilight; a particular type of twilight which is officially defined as civil twilight. This amount of twilight can result in more than 12 hours of usable daylight up to a few weeks before the spring equinox, and up to a few weeks after the fall equinox.
- In a contrary vein, the daylight which is useful for illuminating houses and buildings during the daytime and is needed to produce the full psychological benefit of daylight, is shorter than the nominal time between sunrise and sunset. So in that sense, "useful" daylight is present for 12 hours only after the vernal equinox and before the autumnal equinox, because the intensity of light near sunrise and sunset, even with the sun slightly above the horizon, is considerably less than when the sun is high in the sky.
- It is perhaps valuable for people in the Americas and Asia to know that the equinoxes listed as occurring on March 21, which occurred frequently in the 20th century and which will occur occasionally in the 21st century, are presented as such using UTC, which is at least four hours in advance of any clock in the Americas and as much as twelve hours behind Asian clocks. Thus, there will be no spring equinox later than March 20 in the Americas in the coming century.
"A journey of a thousand miles must begin with a single step." -- Lao Tzu
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