The first calendars based on Zoroastrian cosmology appeared during the later Achaemenian period and though they have evolved and changed over the centuries the names of the months have remained more or less the same till now. Before this period old Persian inscriptions and tablets indicate that early Iranians used a 360-day calendar based on Babylonian system modified according to their own beliefs with their own name days. Month was divided into two or three divisions depending on the phases of the moon. Twelve months were named for various festivals or activities of the pastoral year with 30 days in each month. A thirteenth month every six years was added to keep the 360-day calendar in harmony with the seasons. Under the unified empire of the Achaemenian it was necessary to create a distinctive Iranian calendar based on Zoroastrian beliefs.

In the new calendar following the Egyptian tradition the twelve months and the thirty days were each dedicated to a yazata (Eyzad) with four divisions resembling the Semitic week. Four of the days in the month were dedicated to Ahura Mazda and seven days were named after the six Amesha Spentas. Other thirteen days were named after Fire, the Waters, Sun, Moon, Tiri and Geush Urvan (the soul of all animals), Mithra, Sraosha (Soroush, yazata of prayer), Rashnu (the Judge), Fravashis, Verethraghna (Bahram), Raman (Ramesh meaning peace), and Vata the wind deity. Three were dedicated to female deities, Daena (yazata of religion and personified conscious), Ashi (yazata of fortune) and Arshtat (justice). The remaining four were dedicated to Asman (lord of sky or Heaven), Zam (Earth goddess) and finally Manthra Spenta (the Bounteous Sacred Word, a female deity) and Anaghra Raoch (the ‘Endless Light’ of paradise).

The religious importance of the calendar dedications was very significant. Not only it fixed the pantheon of major deities, but ensured that their names were continuously uttered, since at every Zoroastrian act of worship the deities of both day and month are invoked. With the new system the pattern of festivities became clear as well, Mitrakanna or Mihregan was celebrated on Mithra day of Mithra month or Tiri festival (Tiragan) was celebrated on Tiri day of the Tiri month.

After the conquest of Alexander and his subsequent death the Persian territories fell to one of his generals Seleucus (312 AD) and the Seleucid dynasty of Iran was formed.

Based on the Greek tradition they introduced the practice of dating by era rather than dating by the reign of the individual kings. Their era became known as that of Alexander. The Zoroastrian priests resented Seleucid and found it necessary to create their own era. They had lost their function at the royal courts since the new rulers were not Zoroastrians. They followed the new trend and for the first time started calculating the era of Zoroaster. This was the first serious attempt to establish a historical date for the prophet.

With no Zoroastrian sources at hand they turned to Babylonian archives famous through out the ancient world. From these records they learned that a great event in Persian history took place 228 years before the era of Alexander. The date was 539 BC and in fact is the conquest of Babylon by Cyrus the great.

However the Zoroastrian priests interpreted this date to be the time the true faith was revealed to their prophet and since Avestan literature indicates that revelation happened when Zoroaster was thirty years old, the date of 568 BC was taken to be his birthday. The date entered written records as the beginning of the era of Zoroaster and indeed Persian Empire. This incorrect date is still mentioned in many current Encyclopedias as Zoroaster’s birth date.

Parthians adopted the same system, dated their era from 248 BC, the date they succeeded over the Seleucid and used the same calendar with minor modifications. Their names for the months and days are Parthian equivalencies of the Avestan ones used before and they differ slightly from the Middle Persian names used by the Sassanian. For example in Achaemenian times the modern Persian month ‘Day’ is called Dadvah (Creator), in Parthian it is Datush and Sassanian named it Dadv/Dai (Dadar in Pahlavi).

The next major calendar change happened at the reign of Ardeshir the founder of the Sassanian dynasty in 224 AD. In 46 Ad, Julian the Roman Emperor adopted the Egyptian solar calendar system of 365 days with modifications. Iranians had known about the Egyptian system for centuries but never used it. Ardeshir changed the system to 365 days by adding five extra days at the end and named these ‘Gatha’ or ‘Gah’ days, after the ancient Zoroastrian hymns of the same name. The new system created confusion and met with resistance and is the reason why so many Zoroastrian feasts and celebrations still have two dates. Many rites were practiced over many days instead of one day and duplication of observances was continued to make sure no holy days were missed.

The situation got so complicated that another calendar reform had to be implemented by Ardeshir’s grandson Hormizd I. The new and old holy days were linked together to form continual six-day feasts. No Ruz was an exception. The first and the sixth day of the month were celebrated as different occasions and sixth became more significant as Zoroasters’ birthday rather than a continuation of No Ruz itself. The reform however did not solve all the problems and Yazdegird III, the last ruler, introduced the last changes. Year 631 AD was chosen as the beginning of the new era and the last calendar is known as Yazdegirdi calendar. However they did not get the chance to finish their task. Muslim Arabs overthrew the dynasty in 7^th century AD and with their victory, a new lunar calendar based on Islamic principles replaced the old solar calendar of the Sassanian period.

This calendar was proposed earlier by prophet himself but was first systematically introduced around 638 AD, by the close companion of the Prophet and the second Caliph, Umar ibn Al-Khatab (592-644 AD). This was done to end the conflicting dating systems used at the time. Prophet’s flight from Mecca to Medina (Hijrat) in 622 was chosen as the beginning of the Islamic calendar. The actual starting date for the Calendar was chosen based on lunar years, counting backwards to be the first day of the first month (Muharram) of the first year of the Hijrat. The Islamic (Hijri) calendar is usually abbreviated A.H. in Western languages from the Latin Anno Hegirae.

The twelve lunar months are as follows and the number of days are listed on the right hand side:

Muharram is the start of Muslims’ New Year and the occasion is celebrated by many. Direction to Mecca for praying was chosen on this month. For Shiites this is the most important month of mourning. Imam Husayn, Prophet’s grandson was murdered in the battle of Karbala in this month. Safar is another month of mourning for Shiites since imam Husayn’s mutilated head was taken back to Karbala and the 40^th of his death happens in the same month. The third month marks the flight to Medina and Prophet’s birthday and death. The battle between Ali and Aisha happened on the fifth month. Fatima died on the sixth month. Rajab is the month when ascension (Mi’raj) of prophet to Heaven happened. Muslims believe that Prophet went through a nocturnal journey with Archangel Gabriel. They first went to Jerusalem and then to Heaven and were back on the same night. Imam Husayn was born in Sha’ban. Ramadan is the month of fasting and again a month of mourning for Shiites due to Ali’s assassination in this month. It is also the month Quran was revealed. First day of Shawwal is the major feast of Fitr and the last month is assigned for pilgrimage to Mecca and the feast of Sacrifice (Id i Ghorban). Shiites believe that Ali was appointed by the Prophet to be his rightful successor on this month and celebrate the occasion in the festival of ‘Ghadir Khom’.

 

Being a lunar calendar the months are not related to the solar cycle and therefore do not correspond with the seasons. The festivals move all the time, Ramadan can be in summer or winter or any other season. The lunar year is shorter than the Gregorian year by about 11 days. It is only over a 33-year cycle that the lunar months take a complete turn and fall during the same season. Muslims do not use solar calendars and believe since Prophet has recommended this calendar it should not be changed. Despite the fact that all Muslims are required to use the Islamic lunar calendar Iranians and indeed most Muslim nations for civil duties kept the old solar system to avoid never ending changes in the months and days. Even today most Muslim countries use a solar calendar to avoid complications. The present calendar used in Iran is a solar calendar based on pre-Islamic systems improved in 11^th century during the reign of the Seljuq King, Malak Shah.

 

This calendar is almost unknown in the West, although it is one of the most accurate, if not the most accurate in the world. Compared with the Gregorian calendar, which errs by one day, every 3,226 years, the Iranian calendar needs a one-day correction every 141,000 years. There are two reasons for this accuracy. The Iranian calendar uses a sophisticated intercalation system for determining the leap years. And the beginning of the year, which is a natural phenomenon (arrival of the Sun at the Vernal Equinox), is precisely determined each year by astronomical observations.

The present calendar resulted from a reform conducted in 1079 by a group of astronomers headed by the great Iranian mathematician and poet Omar Khayyam. The origin of the calendar is however much older. It goes back to the Persian Achaemenian period in the 6th century BC. The Islamic lunar calendar was widely used till the end of the 19^th century. However since Pahlavi period the more accurate solar calendar is used throughout the country and has remained the official system despite the Islamic revolution. During Pahlavi period the Arabic months used extensively were abandoned and once again the ancient Persian names were revived and are still in use today.

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