Solar Hijri calendar

The Solar Hijri calendar (Persian: گاه‌شماری هجری خورشیدی‎, romanized: gāhshomāri-ye hejri-ye khorshidi; Pashto: لمريز لېږدیز کلیز‎), also called the Iranian Hijri calendar[1] or Shamsi Hijri calendar, and abbreviated as SH, is the official calendar of Iran and Afghanistan. It begins on the March equinox (Nowruz) as determined by astronomical calculation for the Iran Standard Time meridian (52.5°E, UTC+03:30) and has years of 365 or 366 days.

For the lunar Hijri calendar used to date Islamic holidays and events, see Islamic calendar. For the Late Ottoman-era solar Hijri calendar, see Rumi calendar. For a succession of Iranian solar calendars, see Iranian calendars.
Today
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Its determination of the start of each year is astronomically accurate year-to-year as opposed to the more fixed Gregorian calendar or "Common Era calendar" which, averaged out, has the same year length, achieving the same accuracy (a more simply patterned calendar of 365 days for three consecutive years plus an extra day in the next year, save for exceptions to the latter in three out of every four centuries). The start of the year and its number of days remain fixed to one of the two equinoxes, the astronomically important days which have the same duration of day as night. It results in less variability of all celestial bodies when comparing a specific calendar date from one year to others.[2]

Each of the twelve months corresponds with a zodiac sign. The first six months have 31 days, the next five have 30 days, and the last month has 29 days in usual years but 30 days in leap years. The Iranian New Year's Day always falls on the March equinox.

In Iran
A Persian-language contract published in Tehran on April 14, 1910 which used Lunar Hijri calendar.

On 21 February 1911, the second Iranian parliament adopted as the official calendar of Iran the Jalali sidereal calendar with months bearing the names of the twelve constellations of the zodiac and the years named for the animals of the duodecennial cycle; it remained in use until 1925.[1] 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. It revived the ancient Persian names, which are still used. It specified the origin of the calendar to be the Hegira of Muhammad from Mecca to Medina in 622 CE.[3] It also deprecated the 12-year cycles of the Chinese-Uighur calendar which were not officially sanctioned but were commonly used.

Earlier starting year (1976–1979)

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 Hejra of Muhammad. Overnight, the year changed from 1355 to 2535. The change lasted until the revolution in 1979, at which time the calendar reverted to Solar Hijri.[4]

In Afghanistan

Afghanistan legally adopted the official Jalali calendar in 1922[1] but with different month names. Afghanistan uses Arabic names of the zodiacal signs; for example the 1978 Saur Revolution took place in the second month of the Solar Hijri calendar (Persian Ordibehesht; Saur is named after Taurus). The Solar Hijri calendar is the official calendar of the government of Afghanistan, and all national holidays and administrative issues are fixed according to the Solar Hijri calendar.

Details of the modern calendar

The Solar Hijri 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 March equinox, when the sun enters the Northern Hemisphere. Hence, 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 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. This is a simplification of the Jalali calendar, in which the commencement of the month is tied to the sun's passage from one zodiacal sign to the next. The sun is travelling fastest through the signs in early January (Dey) and slowest in early July (Tir). The current time between the March and September equinoxes is about 186 days and 10 hours, the opposite duration about 178 days, 20 hours.

The Solar Hijri calendar produces a five-year leap year interval after about every seven four-year leap year intervals. It usually follows a 33-year subcycle with occasional interruptions by a single 29-year subcycle, or rarely a 37-year subcycle. The reason for this behaviour is (as explained above) that it tracks the observed vernal equinox. By contrast, some less accurate predictive algorithms are suggested based on confusion between the average tropical year (365.2422 days, approximated with 29-year, 33-year, and 37-year subcycles grouped into 128-year and 132-year cycles and 2820-year great cycles) and the mean interval between spring equinoxes (365.2424 days, approximated with a near 33-year cycle).

Month names
Order Days Iranian Persian Afghan Persian Kurdish Pashto
Native Script Romanized Native Script Romanized Sorani Script Kurmanji Script Native Script Romanized
1 31 فروردین Farvardin حمل Hamal (Aries) خاکەلێوە‎ Xakelêwe وری Wray (Aries)
2 31 اردیبهشت Ordibehesht ثور Sawr (Taurus) گوڵان‎ Gullan (Banemer) غويی Ǧwayay (Taurus)
3 31 خرداد Khordad جوزا Jawzā (Gemini) جۆزەردان‎ Cozerdan غبرګولی Ǧbargolay (Gemini)
4 31 تیر Tir سرطان Saraṭān (Cancer) پووشپەڕ‎ Pûşper چنګاښ Čungāx̌ (Cancer)
5 31 مرداد / امرداد Mordad / Amordad اسد Asad (Leo) گەلاوێژ‎ Gelawêj زمری Zmaray (Leo)
6 31 شهریور Shahrivar سنبله Sonbola (Virgo) خەرمانان‎ Xermanan وږی Waǵay (Virgo)
7 30 مهر Mehr میزان Mizān (Libra) ڕەزبەر‎ Rezber تله Təla (Libra)
8 30 آبان Aban عقرب ʿAqrab (Scorpio) گەڵاڕێزان‎ Xezellwer (Gelarêzan) لړم Laṛam (Scorpio)
9 30 آذر Azar قوس Qaws (Sagittarius) سەرماوەز‎ Sermawez ليندۍ Līndəi (Sagittarius)
10 30 دی Dey جدی Jadi (Capricorn) بەفرانبار‎ Befranbar مرغومی Marǧūmay (Capricorn)
11 30 بهمن Bahman دلو Dalvæ (Aquarius) ڕێبەندان‎ Rêbendan سلواغه Salwāǧa (Aquarius)
12 29/30 اسفند / اسپند Esfand / Espand حوت Hūt (Pisces) ڕەشەمە‎ Reşeme كب Kab (Pisces)

The first day of the calendar year, Nowruz ("New Day"), is the greatest festival of the year in Iran, Afghanistan and surrounding regions. The celebration is filled with many festivities and runs a course of 13 days, the last day of which is called siz-dah bedar ("13 to outdoor").

The Afghan Persian month names are the signs of Zodiac. They were used in Iran in early 20th century when the solar calendar was being used.

Days of the week

In the Iranian calendar, every week begins on Saturday and ends on Friday. The names of the days of the week are as follows: shambe (natively spelled "shanbeh", شنبه), yekshambe, doshambe, seshambe, chæharshambe, panjshambe and jom'e (yek, do, se, chæhar, and panj are the Persian words for the numbers one through five). The name for Friday, jom'e, is Arabic (جمعه). Jom'e is sometimes referred to by the native Persian name, adineh [ɒːdiːne] (آدینه). In some Islamic countries, Friday is the weekly 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.

Solar Hijri and Gregorian calendars

The Solar Hijri year begins about 21 March of each Gregorian year and ends about 20 March of the next year. To convert the Solar Hijri year into the equivalent Gregorian year add 621 or 622 years to the Solar Hijri year depending on whether the Solar Hijri year has or has not begun.

Correspondence of Solar Hijri and Gregorian calendars (Solar Hijri leap years are marked *)[5]
33-year
cycle[6]		Solar Hijri yearGregorian yearSolar Hijri yearGregorian year
11354*21 March 1975 – 20 March 19761387*20 March 2008 – 20 March 2009
2135521 March 1976 – 20 March 1977138821 March 2009 – 20 March 2010
3135621 March 1977 – 20 March 1978138921 March 2010 – 20 March 2011
4135721 March 1978 – 20 March 1979139021 March 2011 – 19 March 2012
51358*21 March 1979 – 20 March 19801391*20 March 2012 – 20 March 2013
6135921 March 1980 – 20 March 1981139221 March 2013 – 20 March 2014
7136021 March 1981 – 20 March 1982139321 March 2014 – 20 March 2015
8136121 March 1982 – 20 March 1983139421 March 2015 – 19 March 2016
91362*21 March 1983 – 20 March 19841395*20 March 2016 – 20 March 2017
10136321 March 1984 – 20 March 1985139621 March 2017 – 20 March 2018
11136421 March 1985 – 20 March 1986139721 March 2018 – 20 March 2019
12136521 March 1986 – 20 March 1987139821 March 2019 – 19 March 2020
131366*21 March 1987 – 20 March 19881399*20 March 2020 – 20 March 2021
14136721 March 1988 – 20 March 1989140021 March 2021 – 20 March 2022
15136821 March 1989 – 20 March 1990140121 March 2022 – 20 March 2023
16136921 March 1990 – 20 March 1991140221 March 2023 – 19 March 2024
171370*21 March 1991 – 20 March 19921403*20 March 2024 – 20 March 2025
18137121 March 1992 – 20 March 1993140421 March 2025 – 20 March 2026
19137221 March 1993 – 20 March 1994140521 March 2026 – 20 March 2027
20137321 March 1994 – 20 March 1995140621 March 2027 – 19 March 2028
21137421 March 1995 – 19 March 1996140720 March 2028 – 19 March 2029
221375*20 March 1996 – 20 March 19971408*20 March 2029 – 20 March 2030
23137621 March 1997 – 20 March 1998140921 March 2030 – 20 March 2031
24137721 March 1998 – 20 March 1999141021 March 2031 – 19 March 2032
25137821 March 1999 – 19 March 2000141120 March 2032 – 19 March 2033
261379*20 March 2000 – 20 March 20011412*20 March 2033 – 20 March 2034
27138021 March 2001 – 20 March 2002141321 March 2034 – 20 March 2035
28138121 March 2002 – 20 March 2003141421 March 2035 – 19 March 2036
29138221 March 2003 – 19 March 2004141520 March 2036 – 19 March 2037
301383*20 March 2004 – 20 March 20051416*20 March 2037 – 20 March 2038
31138421 March 2005 – 20 March 2006141721 March 2038 – 20 March 2039
32138521 March 2006 – 20 March 2007141821 March 2039 – 19 March 2040
33138621 March 2007 – 19 March 2008141920 March 2040 – 19 March 2041

Solar Hijri algorithmic calendar

The Solar Hijri (Persian) calendar is one of the oldest calendars in the world, as well as the most accurate solar calendar in use today. Since the calendar uses astronomical calculation for determining the vernal equinox, it has no intrinsic error, but this makes it an observation-based calendar.[7][8][9][10]

Birashk leap year algorithm

Iranian mathematician Ahmad Birashk (1907-2002) proposed an alternative means of determining leap years. Birashk's book came out in 1993, and his algorithm was based on the same apparently erroneous presumptions as used by Zabih Behruz in his book from 1952.[2] Birashk's technique avoids the need to determine the moment of the astronomical equinox, replacing it with a very complex leap year structure. Years are grouped into cycles which begin with four normal years after which every fourth subsequent year in the cycle is a leap year. Cycles are grouped into grand cycles of either 128 years (composed of cycles of 29, 33, 33, and 33 years) or 132 years, containing cycles of 29, 33, 33, and 37 years. A great grand cycle is composed of 21 consecutive 128-year grand cycles and a final 132 grand cycle, for a total of 2820 years. The pattern of normal and leap years which began in 1925 will not repeat until the year 4745.

Accuracy of the Birashk algorithm

The accuracy of the system proposed by Birashk and other recent authors, such as Zabih Behruz, has been thoroughly refuted and shown to be less precise than the traditional 33-year cycle.[2]

Each 2820-year great grand cycle proposed by Birashk contains 2137 normal years of 365 days and 683 leap years of 366 days, with the average year length over the great grand cycle of 365.24219852. This average is just 0.00000026 (2.6×10−7) of a day shorter than Newcomb's value for the mean tropical year of 365.24219878 days, but differs considerably more from the mean vernal equinox year of 365.242362 days, which means that the new year, intended to fall on the vernal equinox, would drift by half a day over the course of a cycle.[2]

gollark: Arch seems to still have it.
gollark: Now to figure out how to make an actual VM work.
gollark: Ah, of course, the container's not got that.
gollark: _ponders running that on something_
gollark: Very dull.

See also

References
  1. ""Calendars" in ''Encyclopaedia Iranica''". Iranicaonline.org. Retrieved 11 August 2012.
  2. M. Heydari-Malayeri, A concise review of the Iranian calendar, Paris Observatory.
  3. Fazlur Rehman Shaikh, Chronology of Prophetic Events (London: Ta-Ha Publishers Ltd., 2001), p. 157.
  4. Persian Pilgrimages by Afshin Molavi. Books.google.com. Retrieved 11 August 2012.
  5. Holger Oertel (30 May 2009). "Persian calendar by Holger Oertel". Ortelius.de. Archived from the original on 16 July 2012. Retrieved 11 August 2012.
  6. The Persian calendar for 3000 years, (Kazimierz M Borkowski), Earth, Moon, and Planets, 74 (1996), No. 3, pp 223–230. Available at .
  7. "BBCPersian.com". Bbc.co.uk. Retrieved 6 July 2013.
  8. "BBCPersian.com". Bbc.co.uk. Retrieved 6 July 2013.
  9. "پژوهش‌های ایرانی | پاسداشت گاهشماری ایرانی". Ghiasabadi.com. Retrieved 6 July 2013.
  10. "پژوهش‌های ایرانی | گاهشماری تقویم جلالی". Ghiasabadi.com. Retrieved 6 July 2013.

Bibliography
Online calendars and converters
Programming

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