Iranian calendar

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The Iranian calendar or Solar Hejri (Persian: تقویم هجری شمسی؛ گاه‌شماری هجری خورشيدی, Taqwim Hejri Shamsi, Salnamay Hejri Khurshidi) 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.

The Jalali calendar (Persian: گاه‌شماری جلالی), 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] Month computations were based on solar transits through the zodiac, a system integrating ideas from the Surya Siddhanta (India, 4th century).^{[citation needed]} Later, some ideas from the Chinese-Uighur calendar (1258) were also incorporated.^{[citation needed]} It 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 1388 (AP = Anno Persico/Anno Persarum = Persian year). The Iranian year usually begins on 21 March 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.

[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:

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 has always been a symbol in Iranian culture and closely related to the memory of Cyrus the Great himself.

[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 BCE). 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 BCE), 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 BCE. 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 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.

[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 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).

In 224 CE, 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 BCE, 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 Sunni Muslims, but not of the majority Shia Muslims in Iran, 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 15 March 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 century), 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 full ephemeris computations and actual observations to determine the apparent movement of the Sun. Some claim that simplifications introduced in the intervening years may have introduced a system with eight 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 computed the length of a solar year as 365.24219858156 days.^[1] Although this result was poor for 1079, the changing length of the mean tropical year would make it correct about 820 years later:

• 365.2422464 days in 1079^[2]
• 365.2421988 days at 1900.0
• 365.2421897 days at 2000.0

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 21 February 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 31 March 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 (the time between the vernal equinox and the autumnal equinox is about 186 days and 10 hours, the opposite duration about 178 days, 20 hours).^{[citation needed]}

Afghanistan legally adopted this calendar in 1957,^{[citation needed]} but with different month names. The Afghan Pashto language in Afghanistan uses the Pashto names of the zodiac signs. The Afghan Dari language in Afghanistan, uses the Dari 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

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 (two morphemes: know (new) and rooz (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: shanbeh (Saturday, شنبه in native script), yekshanbeh (1 + Saturday = Sunday, یکشنبه), doshanbeh (2 + Saturday = Monday, دوشنبه, see also Dushanbe that means Monday [market]), seshanbeh (3 + Saturday = Tuesday, سه شنبه), chahårshanbeh (4 + Saturday = Wednesday, چهارشنبه), panjshanbeh (5 + Saturday = Thursday, پنجشنبه), and jomhe (Friday, جمعه originally in Arabic) or ådineh (آدینه) (in Persian). In most Islamic countries, jum'a 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. 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

[edit] External links

• Iranian/Persian Calendar/Convertor Persian, Islamic and Gregorian calendar in one, up to 2011
• Persian(Hijri Shamsi) Calendar Gadget Persian/Islamic/Gregorian Calendar Gadget for Windows Vista Sidebar with Persian Occasions. Powerful Convertor with Occasions.
• Persian Multi Calendar This is a free and open source calendar program running under Windows, containing all three calendars Jalali (Persian), Hijri (Islamic) and Gregorian with much more features.
• An Iranian calendar toolbar for Internet Explorer and Firefox
• Online Persian Calendar from aaahoo portal
• Online Persian Calendar Generator and Convertor
• Online Afghan Calendar with Gregorian, Hejrah-e shamsi and Hejrah-e qamari dates
• An online Jalali(shamsi)/Gregorian/Islamic(hijri) Date Convertor
• The Persian Calendar : How the leap years are calculated
• System.Globalization.PersianCalendar class documentation in MSDN Library (The implementation of Persian Calendar in Microsoft .NET Framework 2.0)
• An Interactive Iranian Calendar
• An online Persian/Gregorian date convertor, Persian calendar for mobile (j2me)
• The Zoroastrian Calendar
• Meaning of the names of the months in the Persian Calendar
• Iranian Calendar implemented in JavaScript
• Sun Calendar This is a Persian solar calendar plus some useful tools such as date converters.