Solar Hijri calendar

The Solar Hijri calendar is the official calendar of Iran. It is a solar calendar, based on the Earth's orbit around the Sun. Each year begins on the day of the March equinox and has years of 365 or 366 days. It is sometimes also called the Shamsi calendar, Khorshidi calendar or Persian calendar. It is abbreviated as SH, HS, AP, or, sometimes as AHSh, while the lunar Hijri calendar (commonly known in the West as the 'Islamic calendar') is usually abbreviated as AH.

The epoch (very first day) of the Solar Hijri calendar was the day of the spring equinox, March 19, 622 CE. The calendar is a "Hijri calendar" because that was the year that Mohammed is believed to have left from Mecca to Medina, which event is referred to as the Hijrah.

Since the calendar uses astronomical observations and calculations for determining the vernal equinox, it theoretically has no intrinsic error in matching the vernal equinox year. According to Iranian studies, it is older than the lunar Hijri calendar used by the majority of Muslims (known in the West as the Islamic calendar); though they both count from the year of the Hijrah. The solar Hijri calendar uses solar years and is calculated based on the "year of the Hijrah," and the lunar Hijri calendar is based on lunar months, and dates from the presumed actual "day of the Hijrah".

Each of the twelve months of the solar Hijri calendar corresponds with a zodiac sign. In Iran before 1925 and in Afghanistan before 2023, the names of the zodiacal signs were used for the months; elsewhere the month names are the same as in the Zoroastrian calendar. The first six months have 31 days, the next five have 30 days, and the last month has 29 days in common years, 30 in leap years.

The ancient Iranian New Year's Day, which is called Nowruz, always falls on the March equinox. Nowruz is celebrated by communities in a wide range of countries from the Balkans to Central Asia. Currently the Solar Hijri calendar is officially used only in Iran.

Structure

Epochal date

The calendar's epoch (first year) corresponds to the ''Hijrah'' in 622 CE, which is the same as the epoch of the Lunar Hijri calendar but as it is a solar calendar, the two calendars' year numbers do not coincide with each other and are slowly drifting apart, being about 43 years apart as of 2023.

Days per month

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 in common years 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, due to the eccentricity of Earth's orbit. (These times will change slowly due to precession of the Earth's apsides, becoming inverted after around 11 500 years.)

Leap years

The Iranian Solar 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. The reason for this behaviour is (as explained above) that it tracks the observed vernal equinox.

Some predictive algorithms had been suggested, but were inaccurate due to confusion between the average tropical year (365.2422 days) and the mean interval between spring equinoxes (365.2424 days). These algorithms are not generally used (see Accuracy).

New Year's Day

The Iranian Solar calendar year begins at the start of spring in the Northern Hemisphere: on the midnight in the interval between the two consecutive solar noons that includes the instant of the March equinox. (The solar noon is calculated based on the meridian used for standard time in Iran.) Hence, the first mid-day is on the last day of one calendar year, and the second mid-day is on the first day ( Nowruz) of the next year.

Months

The first day of the calendar year, Nowruz ("New Day"), is the greatest festival of the year in Iran, Afghanistan, and some surrounding historically Persian-influenced regions. The celebration is filled with many festivities and runs a course of 13 days, the last day of which is called (; "outdoor 13th"), or formally Nature Day ().

The Dari (Afghan Persian) month names are the signs of Zodiac. They were used in Iran in the 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: ''shanbeh'', ''yekshanbeh'', ''doshanbeh'', ''seshanbeh'', ''chahārshanbeh'', ''panjshanbeh'' and ''jom'eh''. ''Yek'', ''do'', ''se'', ''chahār'', and ''panj'' are the Persian words for the numbers one to five. The name for Friday, ''jom'eh'', comes from Arabic (.) ''Jom'eh'' is sometimes referred to by the native Persian name, ''ādineh'' (). In some Islamic countries, like Iran and Afghanistan, 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.

Current usage

As of 2024 CE, the only official user of the calendar is Iran.

Iran

On 21 February 1911, the second Iranian parliament adopted as the official calendar of Iran a sidereal calendar with months bearing the names of the twelve constellations of the zodiac and month lengths varying based on the astronomical events; it remained in use until March 1925. The present Iranian calendar was legally adopted on 31 March 1925, the last year of the Qajar era. The law stated 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 also officially set the epoch to the Hijrah, although that epoch was already in use since the 1911 law. It also deprecated the 12-year cycles of the Chinese-Uighur calendar, which were not officially sanctioned but were commonly used.

Afghanistan

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

However, the Taliban imposed the lunar Hijri calendar in Afghanistan during both periods of their rule. Under the Taliban's first rule from 1996 to 2001, the lunar Hijri calendar was imposed, thus changing the year overnight from 1375 to 1417. With effect from 1 Muharram 1444 AH (8Mordad1401 SH; 30July 2022 CE) (the Islamic New Year of the lunar Hijri calendar), the Taliban once again imposed the lunar calendar. Thus the year number once again leaped forward, this time from 1401 to 1444.

Tajikistan

Tajikistan does not use the Solar Hijri calendar and has never done so, despite being part of the Persian-speaking world. The country does, however, celebrate Nowruz, although the official New Year's Day in Tajikistan is 1 January in the Gregorian calendar, which is also the case in other non-Persian speaking Iranian or Turkic communities ranging from Eastern Europe to Western China. The name of Tajikistan's capital, Dushanbe, is taken from the Solar Hijri calendar and translates to "Monday" in Persian.

Comparison with Gregorian calendar

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.

Accuracy

Its determination of the start of each year is astronomically-determined year-to-year as opposed to the more fixed Gregorian or Common Era calendar which, averaged out, has the same year length, achieving the same accuracy (a differently patterned calendar of 365 days for three consecutive years plus an extra day in the next year, save for three exceptions to the latter in a 400-year cycle). The start of the year and its number of days remain fixed to one of the two equinoxes, the astronomically important days when day and night each have the same duration. It results in less variability of all celestial bodies when comparing a specific calendar date from one year to others.M. Heydari-Malayeri
A concise review of the Iranian calendar
Paris Observatory.

Birashk leap year proposal

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. 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.

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.

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 () 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.

Temporary change of epoch and calendar name in Iran

On 14 March 1975 CE, during the Pahlavi era, the Majlis and Senate of Iran, in a joint session, changed the epoch of the calendar to be the supposed first year of the reign of Cyrus the Great, rather than the Hijrah of Muhammad, a change that established the Shahanshahi calendar. This was done not as a new law, but a joint declaration (قطعنامه). The epoch was carefully chosen so that the ascension of Mohammad Reza Pahlavi to the throne would have happened in the round year 2500. Overnight, the year number changed from 1354 to 2534, a difference of 1180 years.

The change lasted until 27 August 1978 CE, at which time the epoch was reverted back to the Hijrah and the original year numbering was reinstated. The reversion was announced on the first day of the government of Prime Minister Jafar Sharif-Emami, and referenced the fact that that 1925 law that introduced the Solar Hijri calendar was still in effect.

See also

* List of observances set by the Solar Hijri calendar
* Arabic names of Gregorian months
* Assyrian calendar
* Babylonian calendar
* Hebrew calendar
* Indian calendar
* Iranian calendars
* Islamic calendar
* Jalali calendar
* Pre-Islamic Arabian calendar
* Rumi calendar
* Zoroastrian calendar

Notes

References

External links

How the leap years are calculated



; Online calendars and converters

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

Online Persian Calendar and converter from parstimes.com

Online Persian Calendar from aaahoo portal

GFDL Afghan Calendar with Gregorian, Hejrah-e shamsi and Hejrah-e qamari dates

; Programming

GPL Iranian Calendar in JavaScript


System.Globalization.PersianCalendar class documentation in MSDN Library
(The implementation of Persian Calendar in Microsoft .NET Framework 2.0)

Persian Zodiac a free, open source AIR application.

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Specific calendars
Time in Afghanistan

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