Iranians/Persians/Parsis use the Solar Hijri calendar, which is a different calendar from the Gregorian calendar.
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- The Solar Hijri calendar is a modified version of the solar Jalali calendar. The tropical Jalali calendar which inherited some aspects from the Yazdgerdi calendar (Sassanid Era 5-6th century) was adopted on 15 March 1079 by the Seljuk Sultan Jalaluddin MalikShah 1. It was created by the order of his scholarly Persian Variz (prime minister), Nizam al-Molk, based on the recommendations of a committee of astronomers, including Omar Khayyam, at the imperial observatory) in his capital city of Isfahan. In 1925 the Jalali calendar was slightly modified to the Hijri calendar, to address minor calculation issues.
- What is the start date of the Hijri calendar?
It is the date when Mohammed (prophet of Islam) moved (Hijrat) from the city of Mecca to Medina (622 CE).
- Why is the Persian Calendar different from the Arabic calendar, even though they have the same start date?
Iran, Afghanistan – use the Solar/Shamsy Hijri Calendar, while most Arabic Countries use the Ghamari / Lunar Hijri Calendar.
Since a solar year is around 10 days longer than a Lunar year, calendar years are different in these countries. Month names are different also. Iranians use 12 Zodiac style months Farvardin, Ordibehesht, Khordad, Tir, Mordad, Shahrivar, Mehr, Aban, Araz, Dey, Bahman, Esfand, starting from the spring equinox (around March 20/21).