Iranian calendar

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The Iranian calendar (Persian: تقویم هجری شمسی؛ گاهشماری هجری خورشیدی) 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 people 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 1387 (AP = Anno Persico/Anno Persarum = Persian year). The Iranian year usually begins on March 21 of the Gregorian calendar. Add 621 or 622 (depending on the time of the year) to an Iranian year to find the corresponding year of the Gregorian calendar.

Contents

[edit] Public holidays and anniversaries

Main article: Public holidays in Iran
Holidays & Anniversaries in 1386 (March 21, 2007-March 20, 2008) in Iran
Date English name Local name Remarks
11th February Revolution Day
10th March Arba’in-e Hosseini (40th day after Ashura) Arba’in-e Hosseini
18th March Martyrdom of Imam Reza
19th March Demise of Muhammad and Martyrdom of Imam Hassan
20th March Nationalization of the oil industries
21st March to 23rd March Persian New Year Nowruz of ancient Iranian origin
1st April Iranian National Day/Islamic Republic Day Proclamation of the Islamic Republic in 1979
2nd April Nature Day Sizdah Bedar 13th day after the new year, end of festivities for Nowruz
6th April Anniversary of Muhammad and Anniversary of Imam Sadeq
4th June Anniversary of the passing of Imam Khomeini 1989
5th June Anniversary of the uprising against the Shah
18th June Martyrdom of Fatima
28th July Anniversary of Imam Ali
11th August Mission of Muhammad Be'sat
28th August Anniversary of Imam Mahdi
3rd October Martyrdom of Imam Ali
15th October End of Ramadan Eid-e-Fitr
6th November Martyrdom of Imam Sadeq
21st December Shab-e-Yalda
21st December Eid-e-Qorban can vary by 1 day
29th December Eid-e-Ghadeer
There are 22 holidays. Dates for anniversaries are based on the persian calendar, muslim calendar or Zoroastrian calendar; the dates on the Gregorian calendar can vary from year to year.

[edit] Iranian and Gregorian calendars

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:

Gregorian Year Iranian Year
2007-2008 1386
2008-2009 1387
2009-2010 1388

Iran adopted Daylight saving time (DST), again, in 2008.

[edit] History of calendars in Persia

Throughout 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.

[edit] Ancient calendars

Old 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.

[edit] Zoroastrian calendar

The 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.

[edit] Modifications by Parthians, Ardashir I, Hormizd I, Yazdgerd III

The 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. Nowruz 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.

[edit] Islamic calendar

But 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.

[edit] Jalali calendar: 1079

The 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:

  • 1303 AP: 30, 31, 32, 31, 32, 30, 31, 30, 29, 30, 29, and 30 days,
  • 1302 AP: 30, 31, 32, 31, 31, 31, 31, 29, 30, 29, 30, and 30 days.

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:

  • 365.2421986 days: Isfahan team, 1079
  • 365.242196 days: end of the 19th century
  • 365.242190 days: end of 20th c. (today)[1]

However, owing to the variations in month lengths, and also the difficulty in computing the calendar itself, the Iranian calendar was modified to simplify these aspects in 1925 (1304 AP).

[edit] Iranian Calendar Reform: 1925

On February 21, 1911, the second Persian parliament mandated government use of a simplified calendric computation system based on the solar calendar. The present Iranian calendar was legally adopted on March 31, 1925, under the early Pahlavi dynasty. The law said that the first day of the year should be the first day of spring in "the true solar year", "as it has been" (کماکان). It also fixed the number of days in each month, which previously varied by year with the tropical zodiac. It revived the ancient Persian names, which are still used. It specified the origin of the calendar (Hegira of Muhammad from Mecca to Medina in 622 CE). It also deprecated the 12-year cycles of the Chinese-Uighur calendar which were not officially sanctioned but were commonly used.

The first six months (Farvardin–Shahrivar) have 31 days, the next five (Mehr–Bahman) have 30 days, and the last month (Esfand) has 29 days or 30 days in leap years. The reason the first six months have 31 days and the rest 30 may have to do with the fact that the sun moves slightly more slowly along the ecliptic in the northern spring and summer than in the northern autumn and winter.[citation needed]

Afghanistan legally adopted this calendar in 1957,[citation needed] but with different month names. The Dari dialect of Persian language in Afghanistan uses the Arabic names of the zodiac signs; these names were also used in Iran before 1925. Afghan Pashto language uses the Pashto names of the zodiac signs.

The Persian calendar produces a five-year leap year interval after about every seven four-year leap year intervals. It usually follows a 33-year cycle with occasional interruptions by single 29-year or 37-year subcycles. By contrast, some less accurate predictive algorithms are suggestion based on confusion between average tropical year (365.2422 days, approximated with near 128-year cycles or 2820-year great cycles) and the mean interval between spring equinoxes (365.2424 days, approximated with a near 33-year cycle).

[edit] Details

The Iranian calendar year begins at the start of Spring in the northern hemisphere: on the midnight between the two consecutive solar noons which include the instant of the Northern spring equinox, when the sun enters the northern hemisphere. If between two consecutive noons the sun's altitude rises through its equinoctial altitude, then the first noon is on the last day of one calendar year and the second noon is on the first day (Nowruz) of the next year. The calendar has 12 months with Persian names.

[edit] Month names

Order Days Persian Kurdish Dari
(Variety of Persian in Afghanistan)		 Afghan Pashto
IPA Native Script Romanized Native Script Romanized Native Script IPA Native Script
1 31 farvardin فروردین Xakelêwe خاكه ليوه hamal (Aries) حمل wraj وری
2 31 ordibeheʃt اردیبهشت Golan گولا ن sawr (Taurus) ثور ʁwajaj غویی
3 31 xordɒd خرداد Jozerdan جوزه ردان dʒawzɒ (Gemini) جوزا ʁbargolaj غبرګولی
4 31 tir تیر Poshper پووش په ر saratɒn (Cancer) سرطان tʃungaʂ چنګاښ
5 31 mordɒd / amordɒd مرداد / امرداد Gelawêj گلاويژ asad (Leo) اسد zmaraj زمری
6 31 ʃahrivar شهریور Xermanan خه رمانان sonbola (Virgo) سنبله wagaj وږی
7 30 mehr مهر Rezber ره زه به ر mizɒn (Libra) میزان təla تله
8 30 ɒbɒn آبان Gelarêzan گه لا ريژان haqrab (Scorpio) عقرب laɻam لړم
9 30 ɒzar آذر Sermawez سه ر ما وه ز qaws (Sagittarius) قوس lindəj لیندۍ
10 30 dej دی Befranbar به فرانبار dʒadi (Capricorn) جدی marʁumaj مرغومی
11 30 bahman بهمن Rêbendan ريبه ندان dalwa (Aquarius) دلو salwɑʁə سلواغه
12 29/30 espand / esfand اسپند / اسفند Resheme ره شه مه howt (Pisces) حوت kab کب

The first day of the calendar year is also the day of the greatest festival of the year in Iran, Afghanistan and surrounding regions, called Nowruz (a single word made up of two parts, now (new) and ruz (day), meaning "new day").

[edit] Days of the week

In the Iranian calendar, every week begins on Saturday and ends on Friday. The days of the week are called: ʃanbeh (شنبه in native script), jekʃanbeh (یکشنبه), doʃanbeh (دوشنبه), seʃanbeh (سه شنبه), tʃahɒrʃanbeh (چهارشنبه), pandʒʃanbeh (پنجشنبه), and dʒomhe (جمعه originally in Arabic) or ɒdineh (آدینه) (in pɒrsi). In most Islamic countries, dʒumʕa is the holiday.

Calculating the day of the week is easy, using an anchor date. One good such date is Sunday, 1 Farvardin 1372, which equals 21 March 1993. Assuming the 33-year cycle approximation, move back by one weekday to jump ahead by one 33-year cycle. Similarly, to jump back by one 33-year cycle, move ahead by one weekday.

As in the Gregorian calendar, dates move forward exactly one day of the week with each passing year, except if there is an intervening leap day when they move two days. The anchor date 1 Farvardin 1372 is chosen so that its 4th, 8th, ..., 32nd anniversaries come immediately after leap days, yet the anchor date itself does not immediately follow a leap day.

[edit] Seasonal error

The image below shows the difference between the Iranian calendar (using the 33-year arithmetic approximation) and the seasons. The Y axis is "days error" and the X axis is Gregorian calendar years. Each point represents a single date on a given year. The error shifts by about 1/4 day per year, and is corrected by a leap year every 4th year regularly, and one 5 year leap period to complete a 33-year cycle. One can notice a gradual shift upwards over the 500 years shown.

Image:Jalaalileap.gif

By comparison, the Gregorian calendar, introduced in 1582, is almost as accurate in the long term, but has larger swings of seasonal errors over centuries.

[edit] References

  1. ^ a b c Omar Khayyam. The MacTutor History of Mathematics archive.

[edit] External links