Iranian Calendars

Officially used in Iran, the Solar Hijri calendar is one of the world’s most accurate calendar systems. It is also known as Persian Calendar, Iranian Calendars, and SH Calendar.

History and Background

The Persian calendar is a solar calendar with a starting point that matches that of the Islamic calendar.  A number of different calendar systems were used in Persia through the centuries, including the Zoroastrian calendar and the Islamic calendar. The first version of the modern Solar Hijri calendar The origin of the Persian calendar can be traced back to the 11th century when a group of astronomers (including the well-known poet Omar Khayyam (created what is known as the Jalaali calendar. However, a number of changes have been made to the calendar since then. The current calendar has been used in Iran since 1925.

When Was Year 1?

The Solar Hijri year count starts with the Islamic prophet Mohammed’s migration (Hegira or Hijrah) to Medina in 622 CE. Although the Solar Hijri calendar shares this start date with the Islamic calendar (Hijri calendar), the calendar systems are not related otherwise.

The Hijri calendar is a lunar calendar. Because of this, the year counts between the Solar Hijri calendar and the Hijri calendar differ substantially. For example, January 1, 2016, fell into the year 1394 in the Solar Hijri calendar, which corresponds to the year 1437 in the Hijri calendar.

The Solar Hijri calendar is not to be confused with the Hijri calendar used in many Muslim countries and by Muslims around the world.

What’s the difference?

Tied to the Equinox

The Solar Hijri calendar is a solar calendar, meaning that its time reckoning is based on the Earth’s movements around the Sun.

Unlike the Gregorian calendar, which follows a set of predetermined rules to stay in sync with the solar year, the Solar Hijri calendar is based on astronomical observations. The year begins at midnight closest to the vernal equinox in Iran – specifically at the Iran Standard Time meridian at longitude 52.5° east, which runs about 250 miles (400 km) east of Tehran. The first day of the new year is called Nowruz, and it is celebrated around the world by Iranian people.

Tying the Solar Hijri calendar so closely to the astronomical seasons makes it much more accurate than the Gregorian calendar, which, even in its modern form.

What does a Persian year look like?

The names and lengths of the 12 months that comprise the Persian year are:

(Due to different transliterations of the Persian alphabet, other spellings of the months are possible.) A year in the Solar Hijri calendar is divided into 12 months of varying lengths. The first 6 months have 31 days, and months 7 through 11 have 30 days. The last month, Esfand has 29 days in a common year and 30 days in a leap year.

When does the Persian year begin?

The Persian year starts at the vernal equinox. If the astronomical vernal equinox falls before noon (Tehran true time) on a particular day, then that day is the first day of the year. If the astronomical vernal equinox falls afternoon, the following day is the first day of the year.

What years are leap years?

Like in the Gregorian calendar, a common year in the Solar Hijri calendar has 365 days while a leap year has 366 days. However, because the Solar Hijri calendar is an observational calendar, there are no mathematical rules to determine leap years. Instead, it is the number of days between two vernal equinoxes that determines if Esfand has 29 or 30 days.

Rule-Based Version

A number of complex mathematical rules have been suggested to determine the distribution of leap years in the Solar Hijri calendar. One of them achieves a degree of accuracy very similar to that of the observational version, requiring about 110,000 years to accumulate an error of 1 day.