Iranian calendar
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The Iranian calendars or Iranian chronology ( fa, گاه‌شماری ایرانی, ) are a succession of calendars invented or used for over two millennia in
Iran Iran, officially the Islamic Republic of Iran, and also called Persia, is a country located in Western Asia. It is bordered by Iraq and Turkey to the west, by Azerbaijan and Armenia to the northwest, by the Caspian Sea and Turkmeni ...
, also known as Persia. One of the longest chronological records in human history, the Iranian calendar has been modified time and again during its history to suit administrative, climatic, and religious purposes. The most influential person in laying the frameworks for the calendar and its precision was the 11th century
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...
polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...
, hakim
Omar Khayyam Ghiyāth al-Dīn Abū al-Fatḥ ʿUmar ibn Ibrāhīm Nīsābūrī (18 May 1048 – 4 December 1131), commonly known as Omar Khayyam ( fa, عمر خیّام), was a polymath, known for his contributions to mathematics, astronomy, philosophy, an ...
. The modern Iranian calendar is currently the official
civil calendar The civil calendar is the calendar, or possibly one of several calendars, used within a country for civil, official, or administrative purposes. The civil calendar is almost always used for general purposes by people and private organizations. Th ...
in Iran and Afghanistan. The Iranian
new year New Year is the time or day currently at which a new calendar year begins and the calendar's year count increments by one. Many cultures celebrate the event in some manner. In the Gregorian calendar, the most widely used calendar system to ...
begins at the midnight nearest to the instant of the northern spring equinox, as determined by astronomic calculations for the meridian (52.5°E). It is, therefore, an observation-based calendar, unlike the Gregorian, which is rule-based. This equinox occurs on or about 20 March of the Gregorian calendar. The
time zone A time zone is an area which observes a uniform standard time for legal, commercial and social purposes. Time zones tend to follow the boundaries between countries and their subdivisions instead of strictly following longitude, because it ...
of Iran is
Iran Standard Time Iran Standard Time (IRST) or Iran Time (IT) is the time zone used in Iran. Iran uses a UTC offset UTC+03:30. IRST is defined by the 52.5 degrees east meridian, the same meridian which defines the Iranian calendar and is the official meridian of ...
, UTC+03:30.


History


Ancient calendars

The earliest evidence of Iranian calendrical traditions is from the second millennium BC and possibly even predates the appearance of the Iranian prophet Zoroaster. The first fully preserved calendar is that of the Achaemenids, a royal dynasty of the 5th century BC who gave rise to Zoroastrianism. Throughout recorded history,
Persians The Persians are an Iranian ethnic group who comprise over half of the population of Iran. They share a common cultural system and are native speakers of the Persian language as well as of the languages that are closely related to Persian. ...
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 favoured a solar over lunar and lunisolar approaches. The sun has always been a religious and divine symbol in Iranian culture and is the origin of the folklore regarding Cyrus the Great..


Old Persian calendar

Old Persian inscriptions and tablets indicate that early Iranians used a
360-day calendar The 360-day calendar is a method of measuring durations used in financial markets, in computer models, in ancient literature, and in prophetic literary genres. It is based on merging the three major calendar systems into one complex clock, with ...
based on the solar observation directly and modified for their beliefs. Days were not named. The 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. An intercalation month was added periodically to keep the calendar synchronized with the seasons. The following table lists the Old Persian months, alongside the approximate Gregorian months and approximate Babylonian
lunar months In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...
. There were four farming festivals, symmetric about ''maidyoshahem'': Two more festivals were later added, creating the six ''gahanbar'':


Zoroastrian calendar

The first calendars based on Zoroastrian cosmology appeared in the later Achaemenid period (650 to 330 BC). They evolved over the centuries, but month names changed little until now. The unified Achaemenid Empire required a distinctive Iranian calendar, and one was devised in
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
ian tradition, with 12 months of 30 days, each dedicated to a
yazata Yazata ( ae, 𐬫𐬀𐬰𐬀𐬙𐬀) is the Avestan word for a Zoroastrian concept with a wide range of meanings but generally signifying (or used as an epithet of) a divinity. The term literally means "worthy of worship or veneration",.. and i ...
(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 Fravashi ( ae, 𐬟𐬭𐬀𐬎𐬎𐬀𐬴𐬌, translit=fravaṣ̌i, ) is the Avestan language term for the Zoroastrian concept of a personal spirit of an individual, whether dead, living, or yet-unborn. The ''fravashi'' of an individual sends ...
, Bahram (yazata of victory), Raman (Ramesh meaning peace), and Vata, the divinity of the wind. Three were dedicated to the female divinities,
Daena Daēnā () is a Zoroastrian concept representing insight and revelation, hence "conscience" or "religion." Alternately, ''Daena'' is considered to be a divinity, counted among the ''yazata''s. Nomenclature Daena is a feminine noun which translat ...
(yazata of religion and personified conscious),
Ashi Ashi (Avestan: 𐬀𐬴𐬌 ''aṣ̌i/arti'') is the Avestan language word for the Zoroastrian concept of "that which is attained." As the hypostasis of "reward," "recompense," or "capricious luck," ''Ashi'' is also a divinity in the Zoroastria ...
(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 month names and their modern versions are given in the following table. 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 Mehregan ( fa, ) or Jashn-e Mehr ( '' Mithra Festival'') is a Zoroastrian and Iranian festival celebrated to honor the yazata Mithra ( fa, Mehr), which is responsible for friendship, affection and love. Name "Mehregan" is derived from the ...
was celebrated on Mithra day of Mithra month, and the Tiri festival (Tiragan) was celebrated on Tiri day of the Tiri month. In 538 BC Cyrus the Great (uncertain if he was a Zoroastrian) conquered Babylon and the Babylonian luni-solar calendar came into use for civil purposes.
Cambyses Cambyses may refer to: * Cambyses I, King of Anshan 600 to 559 BCE * Cambyses II, King of Persia 530 to 522 BCE * Cambyses, ancient name of the Iori river in the South Caucasus * ''Cambyses'', a tragedy (published 1569) by Thomas Preston (writer) ...
conquered Egypt in 525 BC. He was accompanied by Darius, a Zoroastrian who became ruler of the Persian empire in 517 BC. The Zoroastrians adopted the wandering Egyptian solar calendar of twelve months of thirty days plus five epagomenal days. As their year began in the spring (with the festival of ''norouz'') the ''epagomenai'' were placed just before ''norouz''. In Egypt the star Sirius had significance since every 1460 years (the
Sothic cycle The Sothic cycle or Canicular period is a period of 1,461  Egyptian civil years of 365 days each or 1,460  Julian years averaging 365¼ days each. During a Sothic cycle, the 365-day year loses enough time that the start of its ...
) its heliacal rising (just before sunrise) marked the Egyptian new year and the inundation of the Nile. In Persia also the star had significance, since its heliacal rising there also coincided with the coming of the rain. The fourth Persian month was ''Tishtrya'' (Sirius, rain star). The vernal equinox at Greenwich fell on the first day of the first month from 487 to 483 BC (inclusive). Adopting S H Taqizadeh's date of 28 March 487 BC for the reform the calendar for that year is as follows: The fourth month includes 20 July, the date of the heliacal rising of Sirius. In the first year the people carried on using the old calendar, anticipating festival dates by five days. As each day is named after a god, it is important to observe the celebrations on the right day. Thus the ''fravasis'' festival, which in the old calendar was kept between sunset on 30 Spandarmad and sunrise on 1 Frawardin, was now observed throughout the ''epagomenai''. In the second year of the reform, the old 30 Spandarmad was the new 25 Spandarmad, so from then on the festival covered eleven days, up to the new 1 Frawardin. Five days was considered enough for other festivals, however. In all the lands where the Persian calendar was used the ''epagomenai'' were placed at the end of the year. To offset the difference between the agricultural year and the calendar year (the tax-gathering season began after the harvest) the start of the ''araji'' (land-tax) year was delayed by one month every 120 years. A Roman historian, Quintus Curtius Rufus, describing a ceremony in 333 BC, writes:
The magi were followed by three hundred and sixty-five young men clad in purple robes, equal in number to the days of a whole year; for the Persians also divided the year into that number of days.
After the conquests by
Alexander the Great Alexander III of Macedon ( grc, Ἀλέξανδρος, Alexandros; 20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great, was a king of the ancient Greek kingdom of Macedon. He succeeded his father Philip II to ...
and his death, the Persian territories fell to one of his generals, Seleucus (312 BC), starting the
Seleucid The Seleucid Empire (; grc, Βασιλεία τῶν Σελευκιδῶν, ''Basileía tōn Seleukidōn'') was a Greek state in West Asia that existed during the Hellenistic period from 312 BC to 63 BC. The Seleucid Empire was founded by the ...
dynasty of Iran. Based on the Greek tradition, Seleucids 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 The Seleucid era ("SE") or (literally "year of the Greeks" or "Greek year"), sometimes denoted "AG," was a system of numbering years in use by the Seleucid Empire and other countries among the ancient Hellenistic civilizations. It is sometimes r ...
. 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 III

The
Parthia Parthia ( peo, 𐎱𐎼𐎰𐎺 ''Parθava''; xpr, 𐭐𐭓𐭕𐭅 ''Parθaw''; pal, 𐭯𐭫𐭮𐭥𐭡𐭥 ''Pahlaw'') is a historical region located in northeastern Greater Iran. It was conquered and subjugated by the empire of the Med ...
ns (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 Middle Persian or Pahlavi, also known by its endonym Pārsīk or Pārsīg () in its later form, is a Western Middle Iranian language which became the literary language of the Sasanian Empire. For some time after the Sasanian collapse, Middle ...
names used by the Sassanians. For example, in Achaemenid 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). When in April of AD 224 the Parthian dynasty fell and was replaced by the Sasanid, the new king, Ardashir I, abolished the official Babylonian calendar and replaced it with the Zoroastrian. This involved a correction to the places of the ''gahanbar'', which had slipped back in the seasons since they were fixed. These were placed eight months later, as were the ''epagemonai'', the 'Gatha' or 'Gah' days after the ancient Zoroastrian hymns of the same name. Other countries, such as the Armenians and Choresmians, did not accept the change. The new dates were: In AD 224 the vernal equinox at Greenwich fell at noon on 21 March, which was 22 Shahrewar. Immediately after the reform 21 March corresponded to 27 Shahrewar. Here is the calendar for AD 225–6: The change caused confusion and was immensely unpopular. The new ''epagemonai'' were referred to as "robber days". The people now observed the "Great" ''nowruz'' on 6 Frawardin, which was Zoroaster's birthday and corresponded to 1 Frawardin in the old calendar. The new 1 Frawardin was observed as the "lesser" ''nowruz''. Hormizd I (AD 272–273) made the intervening days into festivals as well. In AD 273, the vernal equinox at 0° fell at 05:00 UTC on 21 March.
Yazdegerd I Yazdegerd I (also spelled Yazdgerd and Yazdgird; pal, 𐭩𐭦𐭣𐭪𐭥𐭲𐭩) was the Sasanian King of Kings () of Iran from 399 to 420. A son of Shapur III (), he succeeded his brother Bahram IV () after the latter's assassination. Yazde ...
reigned from AD 399–420. In AD 400 the equinox fell about 19 March, which was 9 Aban. According to al-Biruni, in that reign there was a double adjustment of the start of the ''araji'' year. The tenth-century astronomer Abu'l-asan Kusyar noted that during the reign of Osrow II (AD 589–628) the sun entered Aries in Adur. This happened throughout his reign. An ''araji'' era was introduced dating from AD 621, and the Yazdegerdi era dates from 16 June AD 632, so the Yazdegerdi era is eleven years behind the ''araji''.


Muslim conquest

The Muslim rulers who took over from the middle of the seventh century used the
Islamic calendar The Hijri calendar ( ar, ٱلتَّقْوِيم ٱلْهِجْرِيّ, translit=al-taqwīm al-hijrī), also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 ...
for administration, which caused hardship because the year was shorter – i.e. a tax which was formerly collected after the harvest would now have to be paid before the harvest. Traditionally it is said that the
caliph A caliphate or khilāfah ( ar, خِلَافَة, ) is an institution or public office under the leadership of an Islamic steward with the title of caliph (; ar, خَلِيفَة , ), a person considered a political-religious successor to th ...
Omar reintroduced the Persian calendar for tax collection purposes. In AD 895 there was another double readjustment of the start of the ''araji'' year. It moved from 1 Frawardin (12 April) to 1 Khordad (11 June). By AD 1006 the vernal equinox, 15 March, was again coinciding with ''nowruz'', 1 Frawardin. In that year, therefore, the ''epagemonai'' were delayed four months, moving from the end of Aban to their old position at the end of Spandarmad. This is the calendar for AD 1006/7: The ''gahanbar'' didn't move quite to their old places, because the fifth moved to 20 Day, which was the old 15 Day, thus increasing the interval between the fourth and fifth to eighty days and reducing the interval between the fifth and sixth to 75 days. The new dates were:


Medieval era: Jalali calendar

In AD 1079, by the order of the Jalal Al-Din Shah Seljuqi, the Islamic Calendar (which was and is based on the lunar system) was replaced in Persia by the calendar of
Omar Khayyam Ghiyāth al-Dīn Abū al-Fatḥ ʿUmar ibn Ibrāhīm Nīsābūrī (18 May 1048 – 4 December 1131), commonly known as Omar Khayyam ( fa, عمر خیّام), was a polymath, known for his contributions to mathematics, astronomy, philosophy, an ...
and was called the Jalali Calendar. Khayyam and his team had worked 8 years in Isfahan, the capital of Iran during the Seljuq dynasty. The research and creation of the Khayyam calendar was financially supported by Jalal Al din Shah. Khayyam designed his calendar in which the beginning of the new year, season and month are aligned and he named the first day of the spring and the new year to be Norooz (also spelled
Nowruz Nowruz ( fa, نوروز, ; ), zh, 诺鲁孜节, ug, نەۋروز, ka, ნოვრუზ, ku, Newroz, he, נורוז, kk, Наурыз, ky, Нооруз, mn, Наурыз, ur, نوروز, tg, Наврӯз, tr, Nevruz, tk, Nowruz, ...
). Before Khayyam's calendar, Norooz was not a fixed day and each year could fall in late winter or early spring. From 15 March 1079, when the calendar had slipped a further eighteen days, the ''araji'' calendar was reformed by repeating the first eighteen days of Frawardin. Thus 14 March was 18 Frawardin ''qadimi'' (old) or ''farsi'' (Persian) and 15 March was 1 Frawardin ''jalali'' or ''maleki'' (royal). This new calendar was astronomically calculated, so that it did not have ''epagemonai'' – the months began when the sun entered a new sign of the zodiac. About 120 years after the reform of AD 1006, when the vernal equinox was starting to fall in Ardawahisht, Zoroastrians made it again coincide with ''nowruz'' by adding a second Spandarmad. This ''Shensai'' calendar was a month behind the ''qadimi'' still used in Persia, being used only by the Zoroastrians in India, the Parsees. On 6 June 1745 (
Old Style Old Style (O.S.) and New Style (N.S.) indicate dating systems before and after a calendar change, respectively. Usually, this is the change from the Julian calendar to the Gregorian calendar as enacted in various European countries between 158 ...
) some Parsees re-adopted the ''qadimi'' calendar, and in 1906 some adopted the ''Fasli'' calendar in which 1 Frawardin was equated with 21 March, so that there was a sixth epagomenal day every four years. In 1911 the ''jalali'' calendar became the official national calendar of Persia. Some Zoroastrians in Persia now use the ''Fasli'' calendar, having begun changing to it in 1930.


Modern calendar: Solar Hijri (SH)

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" ever so. It also fixed the number of days in each month, which previously varied by year with the
sidereal zodiac '' Sidereal'' and ''tropical'' are terms used to describe two different definitions of a year, applied in sidereal solar calendars or tropical solar calendars. In astrology, they refer to two different systems of ecliptic coordinates used to ...
. It revived the ancient Persian names, which are still used. 1 Farvardin is the day whose midnight start is nearest to the instant of vernal equinox. The first six months have 31 days, the next five thirty, and the twelfth has 29 days and 30 in leap years. It specified the origin of the calendar to be the Hijrah of Muhammad from Mecca to Medina in AD 622. It also deprecated the 12-year cycles of the Chinese-Uighur calendar which were not officially sanctioned but were commonly used. In 1976, Shah Mohammad Reza Pahlavi changed the origin of the calendar to the beginning of Cyrus the Great's reign as its first year, rather than the
Hijra Hijra, Hijrah, Hegira, Hejira, Hijrat or Hijri may refer to: Islam * Hijrah (often written as ''Hejira'' in older texts), the migration of Muhammad from Mecca to Medina in 622 CE * Migration to Abyssinia or First Hegira, of Muhammad's followers ...
of
Muhammad Muhammad ( ar, مُحَمَّد;  570 – 8 June 632 CE) was an Arab religious, social, and political leader and the founder of Islam. According to Islamic doctrine, he was a prophet divinely inspired to preach and confirm the mo ...
. Overnight, the year changed from 1355 to 2535. This change only lasted until the
Iranian revolution The Iranian Revolution ( fa, انقلاب ایران, Enqelâb-e Irân, ), also known as the Islamic Revolution ( fa, انقلاب اسلامی, Enqelâb-e Eslâmī), was a series of events that culminated in the overthrow of the Pahlavi dyna ...
in 1979, at which time the calendar reverted to Solar Hijri. Correspondence of Solar Hijri and Gregorian calendars (Solar Hijri leap years are marked *):


See also

*
Solar Hijri calendar The Solar calendar ( fa, گاه‌شماری هجری خورشیدی, Gâhšomâri-ye Xoršidi; ps, لمريز لېږدیز کلیز, lamrez legdez kalhandara; ku, ڕۆژژمێری کۆچیی ھەتاوی, Salnameya Koçberiyê) is a solar c ...
*
Tabarian calendar The Tabarian calendar is the indigenous solar calendar of the Mazandaranis and Gilaks. Months *Une Ma *Arke Ma *De Ma *Vahmane Ma *Nurze Ma *Fardine Ma *Kerche Ma *Hare Ma *Tire Ma *Melare Ma *Shervine Ma ...
*
Armenian calendar Armenian may refer to: * Something of, from, or related to Armenia, a country in the South Caucasus region of Eurasia * Armenians, the national people of Armenia, or people of Armenian descent ** Armenian Diaspora, Armenian communities across the ...
*
Lunar Hijri calendar The Hijri calendar ( ar, ٱلتَّقْوِيم ٱلْهِجْرِيّ, translit=al-taqwīm al-hijrī), also known in English as the Muslim calendar and Islamic calendar, is a lunar calendar consisting of 12 lunar months in a year of 354 or ...
*
Pre-Islamic Arabian calendar Several calendars have been used in pre-Islamic Arabia. Inscriptions of the ancient South Arabian calendars reveal the use of a number of local calendars. At least some of these South Arabian calendars followed the lunisolar system. For Central Ar ...
* Assyrian calendar *
Mandaean calendar The Mandaean calendar is a 365-day solar calendar used by the Mandaean people.Drower, Ethel Stefana. ''The Mandaeans of Iraq and Iran''. Oxford At The Clarendon Press, 1937. It consists of twelve 30-day months, with five extra days at the end of ...
* Hebrew calendar *
Babylonian calendar The Babylonian calendar was a lunisolar calendar with years consisting of 12 lunar months, each beginning when a new crescent moon was first sighted low on the western horizon at sunset, plus an intercalary month inserted as needed by decree. Th ...
* Anno Graecorum *
Rumi calendar The ''Rumi'' calendar ( ota, رومي تقویم, , lit. "Roman calendar"), a specific calendar based on the Julian calendar, was officially used by the Ottoman Empire after Tanzimat (1839) and by its successor, the Republic of Turkey until 192 ...
* Royal stars * Shanbeh


References


Citations


Bibliography

* * Taqîzâda, Sayyid Ḥasan, Gâhshumârî dar Îrân-i qadîm, Tehran (Čapkhâna-yi Majlis) 1316/1937-1938, (reprinted with the author's notes appointed to the first edition in the 10th vol. of the Opera omnia, ed.by Î. Afshâr, Tehran, 1357/1978-79). Complete Italian ed.: H. Taqizadeh, Il computo del tempo nell'Iran antico, ed. and transl. by S. Cristoforetti, Roma (ISIAO), 2010.


External links


How the leap years are calculated



Persian(shamsi)/Gregorian/Islamic(hijri) Windows Gadget – with persian occasions
; Online calendars and converters
PersDay.com: Online Persian Calendar and Memo Book Web Application specially designed for Iranians, shows Persian(Hijri-Shamsi), Gregorian, and Hijri-Ghamari calendars for each day; Users can write different types of notes for each day, week, month, season, or year.

An online Persian(shamsi)/Gregorian/Islamic(hijri) date converter on http://www.iranchamber.com

Online Persian Calendar from aaahoo portal

Online Persian Calendar from parstimes.com portal

An online simple Shamsi/Gregorian date converter
; Programming
GPL Iranian Calendar in JavaScript

System.Globalization.PersianCalendar class documentation in MSDN Library
(The implementation of the Persian Calendar in Microsoft .NET Framework 2.0)
Persian Zodiac a free, open source AIR application.

JalaliCalendar (The implementation of the Persian Calendar in java)
{{DEFAULTSORT:Iranian Calendar * Calendars Calendar
Calendars A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a ph ...
Specific calendars Iranian inventions