Nowruz

Nowruz falls at the vernal equinox, and it falls at the moment of the equinox, not on the day nearest it, not on a fixed date approximating it. Iranian families note the exact time, to the minute, and gather for it.

This is possible because the Solar Hijri calendar is astronomically determined rather than arithmetically approximated. Its year begins at the midnight nearest the instant the sun crosses the celestial equator, as observed for the meridian of Tehran. Whether a year has 365 or 366 days is a consequence of that observation, not of a leap rule. The result is a calendar that does not accumulate error against the tropical year at all, more accurate than the Gregorian, which requires its centurial correction and still drifts by a day in some three thousand years.

The month lengths are regular in a way the Gregorian's are not: the first six months have 31 days, the next five have 30, and the last has 29 or 30. The equinox anchoring means that Nowruz falls on 20, 21 or 22 March in the Gregorian calendar and never wanders further.

Afghanistan used the same calendar with different month names until 2022. A parallel arithmetic version, the Jalali reckoning associated with the reform of 1079 in which Omar Khayyam participated, is the historical ancestor.

Iran adopted the Solar Hijri as its official civil calendar in 1925, counting years from the Hijra but running them solar, which produces year numbers roughly 621 less than the Gregorian and about 40 less than the Islamic lunar year.

Nowruz predates Islam in Iran by a long way and has survived every attempt to suppress or absorb it, which is the most interesting political fact about it.

Its roots are Zoroastrian, and it is one of the tradition's major feasts; the Achaemenid reliefs at Persepolis have been read as depicting a new year audience, though that reading is debated. It is not an Islamic festival, has no basis in the Quran or the hadith, and has been criticised by some Islamic authorities across the centuries as a Persian survival. It nevertheless remained the central festival of Iranian life through the Islamic period, and after the 1979 revolution attempts to reduce its prominence in favour of religious observances were not successful.

It is kept far beyond Iran: in Afghanistan, Tajikistan, Uzbekistan, Azerbaijan, Turkey among Kurdish communities, Iraqi Kurdistan, parts of the Caucasus, India among Parsis and by Bahais, for whom it is a holy day and the end of a fast. UNESCO inscribed it on the intangible heritage list in 2009 and the United Nations recognised 21 March as International Nowruz Day in 2010.

Its customs are unusually well preserved. The haft-sin table sets out seven items whose names begin with the Persian letter S, each with an assigned meaning. Chaharshanbe Suri, the fire-jumping on the eve of the last Wednesday, is explicitly pre-Islamic and has been discouraged by authorities. Sizdah Bedar, the thirteenth day, is spent outdoors.

Among Kurds the festival carries a further and specifically political charge, and its public celebration has at times been restricted or violently policed.