Iranian calendar
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The Iranian calendar (Persian: تقویم هجری شمسی؛ گاهشماری هجری خورشیدی), also known as Persian calendar is an astronomical solar calendar and one of the longest chronological records in history and is currently used in Iran and Afghanistan as the main official calendar. Beginning each year on the vernal equinox as precisely determined by astronomical observations from Tehran (or the 52.5°E meridian, which also defines IRST), this makes it more accurate than the Gregorian Calendar in being synchronized with the solar year, but harder to work out when a particular date would occur before the New Year preceding that date. Some believe that the Jalali calendar, an ancestor of the Iranian calendar, was introduced on 15 March, 1079 by the Seljuk Sultan Jalal al-Din Malik Shah I, based on the recommendations of a committee of astronomers, including Omar Khayyam, at the imperial observatory in his capital city of Isfahan[1]. They mention that the calendar included the most accurate computation of the solar year at the time, and month computations were based on solar transits through the zodiac, a system integrating ideas from the Surya Siddhanta (India, 4th c. AD). Later, some ideas from the Chinese-Uighur calendar (1258) were also incorporated. They also claim that the Jalali calendar remained in use for eight centuries. The official Iranian calendar was last changed in 1925 by a law of the Iranian Majlis to have fixed month lengths for the first eleven months of the year, with only the final month iterating between 29 and 30 days based on the year being leap or not. The current Iranian Calendar year is AP 1386 (AP = Anno Persico/Anno Persarum = Persian year). The Iranian year usually begins on March 21 of the Gregorian calendar. Add 621 to an Iranian year to find the corresponding year as reckoned by the Gregorian calendar.
Public holidays and anniversaries
Iranian year begins from 21 March of each Gregorian year and ends on the 20th of the next year. To convert the Iranian year into Gregorian year add 621 years to the reference year. correspondence of Iranian and Gregorian calendars:
History of calendars in PersiaThroughout recorded history, Persians have been keen on the idea and importance of having a calendar. They were among the first cultures to use a solar calendar, and have long favored a solar over lunar and lunisolar approaches. The Sun was always a symbol in Iranian culture. Ancient calendarsOld Persian inscriptions and tablets indicate that early Iranians used a 360-day calendar based on the Babylonian system and modified for their beliefs and named days. Months had two or three divisions depending on the phase of the moon. Twelve months of 30 days were named for festivals or activities of the pastoral year. A 13th month was added every six years to keep the calendar synchronized with the seasons. Zoroastrian calendarThe first calendars based on Zoroastrian cosmology appeared in the later Achaemenian period (650 to 330 BC). They evolved over the centuries, but month names changed little until now. The unified Achaemenian empire required a distinctive Iranian calendar, and one was devised in Egyptian tradition, with 12 months of 30 days, each dedicated to a yazata (Eyzad), and four divisions resembling the Semitic week. Four days per month were dedicated to Ahura Mazda and seven were named after the six Amesha Spentas. Thirteen days were named after Fire, Water, Sun, Moon, Tiri and Geush Urvan (the soul of all animals), Mithra, Sraosha (Soroush, yazata of prayer), Rashnu (the Judge), Fravashi, Bahram (yazata of victory), Raman (Ramesh meaning peace), and Vata, the divinity of the wind. Three were dedicated to the female divinities, 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), Manthra Spenta (the Bounteous Sacred Word) and Anaghra Raocha (the 'Endless Light' of paradise). The calendar had a significant impact on religious observance. It fixed the pantheon of major divinities, and also ensured that their names were uttered often, since at every Zoroastrian act of worship the yazatas of both day and month were invoked. It also clarified the pattern of festivities; for example, Mitrakanna or Mehregan was celebrated on Mithra day of Mithra month, and the Tiri festival (Tiragan) was celebrated on Tiri day of the Tiri month. After the conquests by Alexander the Great and his death, the Persian territories fell to one of his generals, Seleucus (312 BC), starting the Seleucid dynasty of Iran. Based on the Greek tradition, Seuclids introduced the practice of dating by era rather than by the reign of individual kings. Their era became known as that of Alexander, or later the Seleucid era. Since the new rulers were not Zoroastrians, Zoroastrian priests lost their function at the royal courts, and so resented the Seleucids. Although they began dating by eras, they established their own era of Zoroaster. That was the first serious attempt to determine the dates associated with the prophet Zoroaster's life. Priests had no Zoroastrian historical sources, and so turned to Babylonian archives famous in the ancient world. From these they learned that a great event in Persian history took place 228 years before the era of Alexander. In fact, this was the conquest of Babylon by Cyrus the Great in 539 BC. But the priests misinterpreted 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 30 years old, 568 BC was taken as his year of birth. The date entered written records as the beginning of the era of Zoroaster, and indeed, the Persian Empire. This incorrect date is still mentioned in many current encyclopedias as Zoroaster’s birth date. Modifications by Parthians, Ardashir I, Hormizd I, Yazdgerd IIIThe Parthians (Arsacid dynasty) adopted the same calendar system with minor modifications, and dated their era from 248 BC, the date they succeeded the Seleucids. Their names for the months and days are Parthian equivalents of the Avestan ones used previously, differing slightly from the Middle Persian names used by the Sassanians. For example in Achaemenian times the modern Persian month ‘Day’ was called Dadvah (Creator), in Parthian it was Datush and the Sassanians named it Dadv/Dai (Dadar in Pahlavi). In 224 AD, Ardashir I, founder of the Sassanid dynasty, added five days at the end of the year, and named them ‘Gatha’ or ‘Gah’ days after the ancient Zoroastrian hymns of the same name. This was a modification of the 365-day calendar adopted by Julius Caesar in 46 BC, based on the Egyptian solar calendar. Iranians had known about the Egyptian system for centuries but never used it. The new system created confusion and met resistance. Many rites were practiced over many days to make sure no holy days were missed. To this day many Zoroastrian feasts have two dates. To simplify the situation, Ardeshir’s grandson, Hormizd I, linked the new and old holy days into continual six-day feasts. No Ruz was an exception, as the first and the sixth day of the month were celebrated separately, and the sixth became more significant as Zoroasters’ birthday. But the reform did not solve all the problems, and Yazdgerd III, the last ruler, introduced the final changes. The year 631 was chosen as the beginning of a new era, and this last imperial Persian calendar is known as the Yazdgerdi calendar. Islamic calendarBut before the Yazdgerdi calendar was completed, Muslim Arabs overthrew the dynasty in the 7th century and established the Islamic calendar, a lunar calendar. It was outlined in the Qu'ran, and in the last sermon of Muhammad during his farewell pilgrimage to Mecca. Umar, the second caliph of Islam, began numbering years in AH 17 (638 CE), regarding the first year as the year of Muhammad's Hijra (emigration) from Mecca to Medina, in September 622 CE. The first day of the year continued to be the first day of Muharram. Years of the Islamic calendar are designated AH from the Latin Anno Hegirae (in the year of the Hijra). The Islamic lunar calendar was widely used until the end of the 19th century. Jalali calendar: 1079The Jalali calendar was introduced in the 11th century by a panel of astronomers (including Omar Khayyám) at the imperial observatory in the Seljuk capital of Isfahan. It was a solar calendar, and was designed in response to the seasonal drift in the 354 day Islamic calendar. The work was commissioned in 1073 by the Sultan Jalal al-Din Malik Shah I, one of the Seljuk sultans, and were subject to the turbulent history of the times. Fortunately, the calendar work was completed well before the Sultan's death in 1092, after which the observatory would be abandoned. The calendar was adopted on March 15, 1079, and the calendar era was named Jalali in honor of the Sultan[1]. The year was computed from the vernal equinox, and each month was determined by the transit of the sun into the corresponding zodiac region, a system that incorporated improvements on the ancient Indian system of the Surya Siddhanta(Surya=solar, Siddhanta=analysis, 4th c. CE), also the basis of most Hindu calendars. Since the solar transit times can have 24-hour variations, the length of the months vary slightly in different years (each month can be between 29 and 32 days). For example, the months in two last years of the Jalali calendar had:
Because months were computed based on precise times of solar transit between zodiacal regions, seasonal drift never exceeded one day, and also there was no need for a leap year in the Jalali calendar. However, this calendar was very difficult to compute; it required the full ephemeris computations / actual observations to determine solar motion trajectories. Some claim that simplifications introduced in the intervening years may have introduced a system with 8 leap days in every cycle of 33 years. (Different rules, such as the 2820-year cycle, have also been accredited to Khayyam). However, the original Jalali calendar based on observations (or predictions) of solar transit would not have needed either leap years or seasonal adjustments. The team also came up with the computation of the length of a solar year as 365.24219858156 days. The number of decimal digits reflects their high confidence in this computation. Though it may not have been known at the time, the length of the year is changing in the sixth decimal place over a person's lifetime. Nonetheless, the result is astoundingly accurate: the length of the year at various points are:
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