July 6, 2022
The Persian calendar, also known as the Jalāl calendar (jalāli) or the Iranian calendar, is a solar calendar currently used in Iran and Afghanistan. It determines which leap years are not by means of a numerical rule, but on the basis of the observation of the vernal equinox. This calendar, little known in the Western world, is the most accurate of the widely used ones: while the Gregorian calendar presents an error of one day every 3,226 years, the Persian calendar needs a correction every 141,000 years. In fact, it identifies leap years (years of 366 days) with a sophisticated intercalation procedure; it also sets the beginning of the year in a natural phenomenon, the occurrence of the vernal equinox to be observed from year to year with astronomical measurements. Throughout the history of Persian culture, great importance has been placed on the adoption of an accurate calendar. The Persians were among the first peoples to adopt a solar calendar and preferred the solar cycle to the lunar cycle. This attitude accords with the great symbolic significance attributed to the sun in Persian and later Iranian culture. The Persian calendar was defined as a revision of a very ancient previous system towards the end of the 11th century by a commission of scientists which included Omar Khayyam, one of the greatest mathematicians and astronomers of his time (as well as a poet). The recalibration was carried out during the reign of Jalāl ad-Din Malik Shah Seljuqi, one of the Seljuk sultans and in his honor it was also called the Jalāl calendar, The Persian calendar was reintroduced to Persia in 1922 following the efforts of the Iranian patriot Kay Khosrow Shah Ruh. Afghanistan adopted this calendar in 1957, but using Arabic instead of Persian to denote the months by the signs of the zodiac. The sequence of the months of the Persian calendar is as follows: Farvardin (March 21-April 20) Ordibehešt (April 21-May 21) Xordād (May 22-June 21) Tir (June 22-July 22) Mordād-Amordād (July 23-August 22) Šahrivar (August 23-September 22) Mehr (September 23-October 22) Ābān (October 23-November 21) Āzar (November 22-December 21) Day (December 22-January 20) Bahman (January 21-February 19) Esfand (February 20-March 20) The first 6 months are 31 days, the next 5 months are 30 days, the last month is 29 days, 30 days in leap years.