The Northward equinox (or March equinox) is the equinox on the earth when the Sun appears to cross the celestial equator, heading northward. The Northward equinox is the vernal equinox in the Northern Hemisphere and the autumnal equinox in the Southern Hemisphere.
The equinox can be as early as March 19 or as late as March 21, the precise time being about 5 hours 49 minutes later in a common year, and about 18 hours 11 minutes earlier in a leap year, than in the previous year. It is the balance of common years and leap years that keeps the calendar date of the equinox from drifting more than a day from 20 March each year.
Celebrations:
The Persian Calendar begins each year at the Northward equinox, observationally determined at Tehran.
The Indian National Calendar starts the year on the day next to the Vernal Equinox on March 22 (March 21 in 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.
The Julian 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 tropical year is about 11 minutes and 14 seconds less than that. This had the effect of adding about three quarters of an hour every four years. The effect accumulated from 325 until by the 16th century, when the northern vernal equinox fell on March 10 or 11.
Commemorations:
Abrahamic tradition
The Jewish Passover usually falls on the first full moon after the Northern Hemisphere vernal equinox, although occasionally (7 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 latest possible Easter date in any year is April 25.
West Asia
The Northward equinox marks the first day of various calendars including the Iranian calendar. The ancient Iranian new year's festival of Nowruz 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. These festivities recall the story of creation and the ancient cosmology of Iranian and Persian people. It is also a holiday celebrated in Azerbaijan, Afghanistan, Pakistan, 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 Bahá'í Naw-rúz is stationary; the new year always starts at sunset March 20.
In many Arab countries, Mother's Day is celebrated on the Northward equinox.
World Citizen Day occurs on the Northward equinox.
source: wikipedia
