The History of the Iranian Calendar

Iran’s calendar today, the Solar Hijri calendar, is the product of nearly three thousand years of time-keeping: it uses the twelve month names of the ancient Zoroastrian calendar, begins the year at the spring equinox as the Jalali calendar of Omar Khayyam’s time did in 1079, and counts years from the Prophet Muhammad’s migration to Medina in 622. It was adopted in its present form by Iran’s parliament on 31 March 1925 and is one of the most accurate solar calendars in use.

The ancient calendars

The Achaemenid kings used a lunisolar calendar modelled on the Babylonian one but with Old Persian month names; the Behistun inscription dates Darius’s battles by these months, and the Elamite tablets from Persepolis follow a similar system (see the Persepolis Fortification Tablets).

The calendar that shaped later Iran was the Zoroastrian one, probably introduced in the late Achaemenid period. It had twelve months of thirty days, each month and each day named after a divine being, plus five extra days at the end, the Gatha days, making 365. Many of these names are still in use: Farvardin honours the fravashis, the guardian spirits of the dead; Ordibehesht, Khordad, Mordad, Shahrivar, Bahman and Esfand are named after the Amesha Spentas, the holy immortals of Zoroastrian belief; Mehr is Mithra, Tir is the star-god Tishtrya, Aban the waters and Azar fire. When the name of a day matched the name of its month, Iranians held a festival, such as Mehregan on the day Mehr of the month Mehr. The page on Zoroastrianism through the ages follows the religion behind these names.

A year that wandered

The Zoroastrian year had exactly 365 days, about a quarter of a day short of the solar year, so New Year slipped back by a day every four years. Later sources say the Sasanians corrected this by adding a month every 120 years, but how far this was done in practice is debated. Sasanian dates were counted by the years of each king’s reign. After the fall of the empire, Zoroastrians kept counting from the accession of the last king, Yazdegerd III, in 632 (see Yazdegerd III), and this Yazdegerdi era is still used by Zoroastrians for religious dates.

Islam brought the lunar Hijri calendar of twelve lunar months, about eleven days shorter than the solar year. It governed religious life, but tax collectors needed a solar year tied to the harvest, and Iran’s rulers kept using versions of the old solar calendar for land tax. Because the solar year still had no leap day, Nowruz drifted through the seasons, and medieval rulers adjusted it several times. The scholar al-Biruni described the calendars of Iranians, Greeks, Jews and others in his Chronology of Ancient Nations around 1000 CE, one of the best sources for the old Iranian festivals.

The Jalali reform of 1079

The Seljuk sultan Malik-Shah, advised by his vizier Nizam al-Mulk, commissioned a group of astronomers at Isfahan, among them Omar Khayyam, to fix the problem. The new Jalali calendar, named after the sultan’s title Jalal al-Dawla, came into force on 15 March 1079. It started the year on the day of the vernal equinox, determined by observation, so Nowruz was tied permanently to the first day of spring. Leap years followed from the astronomy rather than from a simple rule, which made the calendar more accurate over long periods than the Gregorian reform of 1582, though harder to calculate in advance. The Jalali calendar was used alongside the lunar Hijri for centuries, mainly for astronomy, taxes and the date of Nowruz.

Many calendars in Qajar Iran

Before the twentieth century an Iranian document could carry several dates. Religious and official dates used the lunar Hijri; the solar year was described with the Arabic names of the zodiac signs (Hamal, Sowr and so on); and from Mongol times the twelve-year animal cycle of Turkic and Chinese origin, with years of the Mouse, Ox, Tiger and so forth, was also used in administration. The almanacs printed each year by court astronomers reconciled them all.

The modern calendar and the Imperial interlude

The second Majlis adopted a solar calendar with zodiac month names on 21 February 1911. On 31 March 1925, in the last months of the Qajar dynasty, parliament passed the law that created the present calendar: solar years counted from the Hijra, months with the old Persian names in place of the zodiac, and a fixed pattern of month lengths in which the six spring and summer months have 31 days, matching the slower movement of the sun across the sky in those seasons.

In March 1976 Mohammad Reza Shah replaced the Hijri epoch with an “Imperial” (shâhanshâhi) era counting from the accession of Cyrus the Great, in the spirit of the 2,500-year celebrations of 1971: overnight the year 1355 became 2535. The change angered religious Iranians and became a grievance of the opposition, and the government reversed it in 1978, months before the revolution.

The calendar today

Iran now uses the Solar Hijri calendar for civil life, the lunar Hijri calendar for religious holidays such as Ramadan and Ashura, which move through the solar year, and the Gregorian calendar for international dealings. The week begins on Saturday, and Friday is the weekly holiday. The exact moment of the equinox, and so the date of Nowruz and of each leap year, is published by Iranian astronomers each year. Our guide to Persian calendar days and months teaches the names you need, and the Persian date converter turns any Gregorian date into its Solar Hijri equivalent. For the festival that opens the year, see Nowruz through history and Iranian festivals and public holidays.

1. c. 520 BCE Behistun inscription dates events by Old Persian months
2. 632 Start of the Yazdegerdi era
3. c. 1000 Al-Biruni’s Chronology of Ancient Nations
4. 15 March 1079 Jalali calendar comes into force
5. 21 February 1911 Majlis adopts an official solar calendar
6. 31 March 1925 Present Solar Hijri calendar adopted with Persian month names
7. 1976–1978 Imperial era from Cyrus replaces the Hijri epoch, then is abandoned