Iranian calendar

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The Iranian calendar (Persian: گاه‌شماری هجری خورشيدى‎) also known as Persian calendar or the Jalāli Calendar is a solar calendar currently used in Iran and Afghanistan. It is observation-based, rather than rule-based, beginning each year on the vernal equinox as precisely determined by astronomical observations from Tehran (or the 52.5°E meridian) and Kabul. This makes it more accurate than Gregorian Calendar, but harder to work out which years are leap years.

1 Background
2 History of calendars in Persia
3 Details
4 Month Names
5 Days of the week in Iranian calendar
6 Calendar seasonal error
7 Calculating the day of the week
8 See also
9 External links

[edit] Background

Persians have been keen on the idea and importance of having a calendar system throughout their recorded history. They were among the first cultures to employ a solar calendar, and have long favored a solar approach rather than lunar or lunisolar models. In general, the sun has always had an important symbolic significance in the Iranian culture.

After a first try by the second Persian parliament on February 21, 1911 which mandated the use of the solar years and months for official governmental use, the present Iranian calendar was legally adopted by the Persian parliament on March 31, 1925, specifying the origin on the calendar (Hegira of Muhammad from Mecca to Medina in 622 CE), mentioning that the beginning of the year is the first day of spring, that the year is the "true solar" year "as it has been" (کماکان), and specifying the month names and the number of days in each month. The law goes further and officially deprecates the 12 year cycles of the Chinese-Uighur calendar which were unofficially but commonly used.

Afghanistan legally adopted the new Iranian calendar in 1957, using the same number of days in each month but different month names. In Afghan Persian (also known as Dari), the Arabic language names of the zodiac signs for the months are used instead of the names adopted in Iran in 1925. (These zodiac names were also used in Iran before 1925.) In Afghan Pashto, native Pashto names of the zodiac signs are used.

[edit] History of calendars in Persia

The first calendars based on Zoroastrian cosmology appeared during the later Achaemenian period (650 to 330 BCE) 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 the Babylonian system modified according to their own beliefs, and their own named days. Months were divided into two or three divisions depending on the phase 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 Achaemenians it was necessary to create a distinctive Iranian calendar, and one was devised based on the Egyptian tradition, with twelve months of thirty days, each dedicated to a yazata (Eyzad), and 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. 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), 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 observations. Not only did it fix the pantheon of major divinities, but ensured that their names were continually uttered, since at every Zoroastrian act of worship the yazatas of both day and month were invoked. With the new system, the pattern of festivities became clear as well. 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 of Alexander the Great and his subsequent death, the Persian territories fell to one of his generals Seleucus (312 BCE) 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, or later the Seleucid era. The Zoroastrian priests, having lost their function at the royal courts since the new rulers were not Zoroastrians, resented the Seleucids. Although they followed the new trend of dating by eras, they established their own era of Zoroaster.

This marked the first serious attempt to determine the dates associated with the prophet Zoroaster's life. With no Zoroastrian historical sources they turned to Babylonian archives famous throughout 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 BCE, which was in fact the conquest of Babylon by Cyrus the Great. The Zoroastrian priests, however, 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 thirty years old, 568 BCE 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.

The Parthians (Arsacid dynasty) adopted the same calendar system with minor modifications, and dated their era from 248 BCE, 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).

The next major calendar change happened during the reign of Ardashir I the founder of the Sassanid dynasty in 224 CE. In 46 CE, Julius Caesar the Roman Emperor, adopted the Egyptian solar calendar system of 365 days with some modifications. Iranians had known about the Egyptian system for centuries but never used it. Ardashir, however, changed the length of the calendar year 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 was met with resistance, and many Zoroastrian feasts and celebrations have two dates, to this day. 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 became 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 as the first and the sixth day of the month were celebrated separately, with the sixth becoming more significant as Zoroasters’ birthday rather than a continuation of No Ruz itself. The reform however did not solve all the problems, and Yazdgerd III, the last ruler, introduced the final changes. The year 631 CE was chosen as the beginning of a new era, and this last imperial Persian calendar is known as the Yazdgerdi calendar. However, before work on the new calendar was completed, Muslim Arabs overthrew the dynasty in the 7th century and with their victory, a new lunar calendar based on Islamic principles replaced the old solar calendar of the Sassanid period.

The Islamic calendar was outlined in the prophet Muhammad's revelation, the Qu'ran, and in his last sermon during his farewell pilgrimage to Mecca. It was the same as the old pagan Meccan calendar except that the intercalary month was eliminated, effective at the end of AH 10 (March 632 CE). Umar, the second caliph, began numbering its years in AH 17 (638 CE), regarding its first year as the year during which Muhammad's Hijra (emmigration) from Mecca to Medina occurred, in September 622 CE. The first day of the year was not changed—it 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 Iranian calendar was revised in the 11th century by a panel of scientists, allegedly including Omar Khayyám. The recalibration was completed during the reign of Jalaal ad-Din Malik Shah Seljuki, one of the Seljuk sultans, and named in his honor.

The Islamic lunar calendar was widely used till the end of the 19th century. During the early Pahlavi era in 1925, the lunar calendar was officially replaced by the modern Iranian calendar. The act of 1925 mentioned that "the true solar year" should be used for computing the first day of the year, and also fixed the number of days in each month (which was previously different in each year, corresponding with the tropical zodiac). It also revived the ancient Persian names, which are still in use today.

[edit] Details

The Iranian calendar year begins 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; in other words, the start of Spring in the northern hemisphere. The calendar consists of twelve months with Persian names. The first six months are 31 days each, the next five 30 days, and the last month has 29 days but 30 days in leap years. The reason the first six months have 31 days and the rest 30 was not a random decision by the designers – it has to do with the fact that the sun moves slightly more slowly along ecliptic in the northern spring and summer than in the northern autumn and winter. It should also be noted that before the adaptation of the modern Persian calendar in 1925 (1304 AP), the length of the months were different each year, and a month could also consist of 32 days. For example, the length of the Persian months in the year 1303 AP were respectively 30, 31, 32, 31, 32, 30, 31, 30, 29, 30, 29, and 30 days, while the length of the months in 1302 AP were 30, 31, 32, 31, 31, 31, 31, 29, 30, 29, 30, and 30 days.

In other words, the Persian new year is determined by noon-time observation of the Northern spring equinox. 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 (Norouz) of the next calendar year.

Typically leap years are devised and used by various solar calendar systems, usually every four years. Four-year leap years add 0.25 day to each year in the period, but that is a slight overcompensation compared to the actual behaviour of the sun. To remedy this overcompensation, after about every seven four-year leap year intervals, the Persian solar calendar produces a five-year leap year interval. It usually follows a thirty-three year cycle with occasional interruptions by single twenty-nine year or thirty-seven year subcycles.

This general picture of the Persian calendar's leap-year behaviour contrasts with less accurate predictive algorithms which are based on confusion between the astronomers 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] Month Names

Order	Days	Iranian/Persian name		Afghan name (Arabic translation of Zodiac signs)		Afghan Pashto name
Order	Days	Latin	Persian	Latin	Arabic	IPA	Pashto
1	31	Farvardin	فروردین	haməl	حمل	wray	وری
2	31	Ordibehesht	اردیبهشت	Sawr	ثور	ʁwayay	غویی
3	31	Khordad	خرداد	Jawza	جوزا	ʁbargolay	غبرګولی
4	31	Tir	تیر	Saratan	سرطان	tʃungaʂ	چنګاښ
5	31	Mordad	مرداد	Asad	اسد	zmaray	زمری
6	31	Shahrivar	شهریور	Sonbola	سنبله	wagay	وږی
7	30	Mehr	مهر	Mizan	میزان	Təla	تله
8	30	Aban	آبان	Aqrab	عقرب	Laɻam	لړم
9	30	Azar	آذر	Qaws	قوس	lindəy	لیندۍ
10	30	Dey	دی	Jady	جدی	marʁumay	مرغومی
11	30	Bahman	بهمن	Dalv	دلو	salwɑʁə	سلواغه
12	29/30	Esfand	اسفند	Hout	حوت	kab	کب

The first day of the calendar year is also the day of the greatest festival of the year in Iran, called Norouz (a single word made up of two parts, no and rouz, meaning "new day").

[edit] Days of the week in Iranian calendar

In Iranian Calendar, every week begins on Saturday and ends on Friday. Names of days of the week are:

Shanbeh (شنبه in Persian) equivalent to Saturday in Gregorian calendar.

Yekshanbeh (یکشنبه in Persian) equivalent to Sunday in Gregorian calendar.

Doshanbeh (دوشنبه in Persian) equivalent to Monday in Gregorian calendar.

Seshanbeh (سه شنبه in Persian) equivalent to Tuesday in Gregorian calendar.

Chaharshanbeh (چهارشنبه in Persian) equivalent to Wednesday in Gregorian calendar.

Panjshanbeh (پنجشنبه in Persian) equivalent to Thursday in Gregorian calendar.

Jom'eh (جمعه in Persian, originally Arabic) or Adineh (آدینه in Persian) equivalent to Friday in Gregorian calendar.

In Islamic countries, Jom'eh is the weekend.

[edit] Calendar seasonal error

In the 11th century, a team of astronomers, allegedly including Omar Khayyam, proposed certain rules. While the details of the exact rule is debated, some claim that it inserted 8 leap days in every cycle of 33 years (different rules, such as the 2820-year cycle have also been accredited to Omar Khayyam). This replaced a previously common calendar that had a leap day every four years, and was adopted by Jalaal ad-Din Malik Shah Seljuki and became known as the Jalaali calendar.

This image 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.

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

[edit] Calculating the day of the week

Calculating the day of the week is easy. You just need an anchor date to start with. One good day to choose is Sunday, 1 Farvardin 1372, which equals 21 March 1993.

Assuming the 33-year cycle approximation, to jump ahead by one 33-year cycle: move back by one weekday. 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. The leap day will make the date move an additional day forward. The chosen 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.