Solar Hijri calendar
It begins on the March equinox as determined by the astronomical calculation for the Iran Standard Time meridian (52.5°E, UTC+03:30) and has years of 365 or 366 days.
[6][7] 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".
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.
[citation needed] (The solar noon is calculated based on the meridian used for standard time in Iran.)
The names of the days of the week are as follows: shanbeh, yekshanbeh, doshanbeh, seshanbeh, chahārshanbeh, panjshanbeh and jom'eh.
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.
[1] The present Iranian calendar was legally adopted on 31 March 1925, the last year of the Qajar era.
Afghanistan legally adopted the official Jalali calendar in 1922[1] but with different month names.
The country does, however, celebrate Nowruz, although the official New Year's Day in Tajikistan is 1 January in the Gregorian calendar,[12] 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.
Iranian mathematician Ahmad Birashk (1907–2002) proposed an alternative means of determining leap years.
[17] Birashk's technique avoids the need to determine the moment of the astronomical equinox, replacing it with a very complex leap year structure.
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.
[17] 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,[1] rather than the Hijrah of Muhammad, a change that established the Shahanshahi calendar.
The epoch was carefully chosen so that the ascension of Mohammad Reza Pahlavi to the throne would have happened in the round year 2500.
The change lasted until 27 August 1978 CE,[e] at which time the epoch was reverted back to the Hijrah and the original year numbering was reinstated.
[1] 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.
