On theGregorian calendar at0° longitude, the northward equinox usually occurs on March 20. However, it can occur as early as March 19 (which happened most recently in 1796, and will happen next in 2044), and it can occur as late as March 21 (which happened most recently in 2007, and will happen next in 2102). For acommon year thecomputed time slippage is about 5 hours 49 minuteslater than the previous year, and for a leap year about 18 hours 11 minutesearlier than the previous year. Balancing the increases of the common years against the losses of the leap years keeps the calendar date of the March equinox from drifting more than one day from March 20 each year.
The March equinox may be taken to mark the beginning ofastronomicalspring and the end of astronomicalwinter in the Northern Hemisphere but marks the beginning of astronomicalautumn and the end of astronomicalsummer in the Southern Hemisphere.[11]
The point where the Sun crosses the celestial equator northwards is called theFirst Point of Aries. However, due to theprecession of the equinoxes, this point is no longer in theconstellationAries, but rather inPisces.[13] By the year 2600 it will be inAquarius. The Earth's axis causes the First Point of Aries to travel westwards across the sky at a rate of roughly one degree every 72 years. Based on themodern constellation boundaries, the northward equinox passed fromTaurus into Aries in the year −1865 (1866 BC), passed into Pisces in the year −67 (68 BC), will pass into Aquarius in the year 2597, and will pass intoCapricornus in the year 4312. It passed by (but not into) a 'corner' ofCetus at 0°10′ distance in the year 1489.[citation needed]
In its apparent motion on the day of an equinox, the Sun's disk crosses the Earth's horizon directly to the east atsunrise; and again, some 12 hours later, directly to the west atsunset. The March equinox, like all equinoxes, is characterized by having an almost exactly equal amount of daylight and night across most latitudes on Earth.[14]
TheIndian national calendar starts the year on the day next to the vernal equinox on March 22 (March 21 during leap years) with a 30-day month (31 days in leap years), then has 5 months of 31 days followed by 6 months of 30 days.[15]
TheJulian calendar reform lengthened seven months and replaced the intercalary month with an intercalary day to be added every four years to February. It was based on a length for the year of 365 days and 6 hours (365.25 d), while the mean tropical year is about 11 minutes and 15 seconds less than that. This had the effect of adding about three quarters of an hour every four years. The effect accumulated from inception in 45 BC and by the 16th century, the northern vernal equinox fell on March 10 or 11.[16] Since the date of the equinox is critical tocalculation of the date of Easter, its drift from astronomical reality was of grave concern to the Catholic church. It was for this reason that theGregorian calendar reform was introduced in 1582, to reinstate the date to about 21 March and to minimise any further drifting. Since 1900, the calendars differ by 13 days: from 1 March 2100, the difference will become 14 days.
Bas-relief inPersepolis, a symbol ofIranianNowruz: a bull (symbolizing the Earth) and lion (the Sun) in eternal combat are equal in power on the equinox.Chichen Itza during the spring equinox—Kukulkan, the famous descent of the snake
The JewishPassover usually falls on the firstfull moon after the Northern Hemisphere vernal equinox,[17] although occasionally (due to accumulated error strictly following the Meton approximation, currently three times every 19 years[citation needed]) it will occur on the second full moon.[18]
TheChristian ChurchescalculateEaster 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. TheEastern Orthodox Churches use the olderJulian calendar, while the western churches use theGregorian calendar, and the western full moons currently fall four, five or 34 days before the eastern ones. The result is that the twoEasters generally fall on different days but they sometimes coincide. The earliest possible western Easter date in any year is March 22 on each calendar. The latest possible western Easter date in any year is April 25.[19]
The northward equinox marks the first day of various calendars including theIranian calendar. The ancient Iranian peoples' new year's festival ofNowruz can be celebrated March 20 or March 21. 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. Along withIranian peoples, it is also a holiday celebrated byTurkic people, theNorth Caucasus and inAlbania. It is also a holiday forZoroastrians, adherents of theBaháʼí Faith andNizariIsmaili Muslims irrespective of ethnicity.[20]
According to thesidereal solar calendar, celebrations which originally coincided with the March equinox now take place throughout South Asia and parts of Southeast Asia on the day when the Sun enters thesidereal Aries, generally around April 14.
The traditional East Asian calendars divide a year into 24solar terms (节气, literally "climatic segments"), and the vernal equinox (Chūnfēn,Chinese andJapanese: 春分; Korean:춘분; Vietnamese:Xuân phân) marks themiddle of the spring. In this context, theChinese character 分 means"(equal) division" (within a season).
In Japan,Vernal Equinox Day (春分の日Shunbun no hi) is an officialnational holiday, and is spent visiting family graves and holding family reunions.[21][22]Higan (お彼岸) is a Buddhist holiday exclusively celebrated by Japanese sects during both the Spring and Autumnal Equinox.[21]
World Storytelling Day is a global celebration of the art of oral storytelling, celebrated every year on the day of the northward equinox.[citation needed]
TheBaháʼí calendar year starts at the sunset preceding the March equinox calculated for Tehran.[29]
InAnnapolis, Maryland, United States, boatyard employees and sailboat owners celebrate the spring equinox with the "Burning of the Socks" festival. Traditionally, the boating community wears socks only during the winter. These are burned at the approach of warmer weather, which brings more customers and work to the area. Officially, nobody then wears socks until the next equinox.[30][31]
