The Persian calendar, explained

What the Persian calendar is

The Persian calendar goes by several names. In Iran it is usually called Hijri Shamsi (“solar Hijri”) or simply Shamsi; you will also see Solar Hijri, Jalali, Khorshidi and Iranian calendar. On ShamsiDate we use Shamsi and Solar Hijri interchangeably.

Two ideas define it:

• Years are counted from 622 CE, the year of the Hijra — the Prophet Muhammad’s migration from Mecca to Medina. This is the same starting point as the Islamic lunar calendar, but the Persian calendar counts solar years, so its year numbers grow more slowly. In November 2026, for example, the Persian year is 1405 while the lunar Hijri year is 1448.
• Each year starts at the March equinox. The new year, Nowruz, is the day the Sun crosses the celestial equator heading north — the first day of spring in the Northern Hemisphere.

It is the official civil calendar of Iran, used on birth certificates, school records, contracts and newspapers. Afghanistan has also used a Solar Hijri calendar, with the same month lengths but zodiac-based month names such as Hamal and Sawr.

See 1 Farvardin 1405 in the converter

Twelve months, four seasons

The year has twelve months grouped into four seasons of three months each. The structure is simple and fixed by law: the first six months have 31 days, the next five have 30, and the last month, Esfand, has 29 days — or 30 in a leap year.

The Solar Hijri months, with their Gregorian dates in 1405 SH (2026–2027)

#	Month	Days	Season	Gregorian span (1405)	Name origin
1	فروردین Farvardin	31	Spring	21 Mar – 20 Apr	The fravashis, guardian spirits of the righteous
2	اردیبهشت Ordibehesht	31	Spring	21 Apr – 21 May	Asha Vahishta, “best truth” or righteousness
3	خرداد Khordad	31	Spring	22 May – 21 Jun	Haurvatat, wholeness and perfection
4	تیر Tir	31	Summer	22 Jun – 22 Jul	Tishtrya, the rain-bringing star Sirius
5	مرداد Mordad	31	Summer	23 Jul – 22 Aug	Ameretat (Amordad), immortality
6	شهریور Shahrivar	31	Summer	23 Aug – 22 Sep	Khshathra Vairya, the desirable dominion
7	مهر Mehr	30	Autumn	23 Sep – 22 Oct	Mithra, covenant and friendship
8	آبان Aban	30	Autumn	23 Oct – 21 Nov	Apas, the waters
9	آذر Azar	30	Autumn	22 Nov – 21 Dec	Atar, fire
10	دی Dey	30	Winter	22 Dec – 20 Jan	Dadvah, the Creator
11	بهمن Bahman	30	Winter	21 Jan – 19 Feb	Vohu Manah, good mind
12	اسفند Esfand	29 or 30	Winter	20 Feb – 20 Mar	Spenta Armaiti, holy devotion, guardian of the earth

Because the calendar starts at the equinox and its months are tied to the Sun, the seasons line up with the months almost perfectly. Spring always starts on 1 Farvardin, summer on 1 Tir, autumn on 1 Mehr and winter on 1 Dey. The night before 1 Dey is Yalda, the longest night of the year, celebrated with family, poetry, pomegranates and watermelon.

• 1 Farvardin March equinox · Nowruz
• 1 Tir June solstice
• 1 Mehr September equinox
• 1 Dey December solstice · Yalda

Why the first six months have 31 days

This isn’t arbitrary. Earth’s orbit is slightly elliptical, and Earth moves a little more slowly when it is farthest from the Sun, in early July. As a result, the Sun takes about 186 days to travel from the March equinox to the September equinox, but only about 179 days to come back. Six months of 31 days add up to exactly 186; five months of 30 days plus a 29-day Esfand add up to 179. The calendar’s month lengths mirror the real length of the astronomical seasons.

Where the month names come from

The month names are much older than the modern calendar. They come from Avestan names of Zoroastrian concepts and divine beings: Farvardin from the fravashis, the guardian spirits; Mehr from Mithra, the guardian of covenants; Aban from the waters; Azar from fire. The Origin column in the table above gives each name’s source.

When Iran’s parliament adopted the modern calendar in 1925, it chose these Persian names to replace the zodiac-based names (Hamal, Sawr, Jawza…) that had been used in official reckoning until then.

Leap years: set by the sky

Most calendars decide leap years with a fixed rule. The Persian calendar is different: a year is a leap year when 366 days separate one Nowruz from the next. Nowruz is the day on which the March equinox occurs before noon Iran time (the 52.5° E meridian); if the equinox falls after noon, Nowruz is the following day. When that rule pushes the next Nowruz one day later than usual, the year gains a 30th day of Esfand.

The result is a strikingly regular pattern. Leap years usually come every four years, but roughly every 33 years the gap stretches to five years. In this era that happens every 33 years: 1370 → 1375, 1403 → 1408, and next 1436 → 1441. A 33-year span typically contains eight leap years.

Weeks and weekends

The Persian week starts on Saturday and Friday is the weekly holiday. Most weekday names simply count from Saturday (shanbeh): yekshanbeh is “one [day after] Saturday”, doshanbeh “two”, and so on through panjshanbeh, Thursday. Friday is jomeh, from the Arabic word for gathering.

Day	Persian	Meaning
Saturday	شنبه · Shanbeh	the Sabbath day
Sunday	یکشنبه · Yekshanbeh	“day one” after Saturday
Monday	دوشنبه · Doshanbeh	“day two”
Tuesday	سه‌شنبه · Seshanbeh	“day three”
Wednesday	چهارشنبه · Chaharshanbeh	“day four”
Thursday	پنجشنبه · Panjshanbeh	“day five”
Friday	جمعه · Jomeh	day of gathering

A short history

The modern calendar is young, but its ingredients — a solar year, a spring new year and the old Iranian month names — are centuries old.

1. 622

   The Hijra sets the year count

   The Persian calendar counts its years from the Prophet Muhammad’s migration to Medina, like the Islamic lunar calendar — but in solar years.

2. 1079

   The Jalali calendar

   The Seljuk sultan Malik-Shah adopts a solar calendar prepared by a committee of astronomers that included Omar Khayyam. It is named after one of his titles, Jalal al-Din, and anchors the year to the spring equinox.

3. 1925

   The modern Solar Hijri calendar

   On 31 March 1925 (11 Farvardin 1304) Iran’s parliament adopts the calendar used today, with Persian month names and fixed month lengths.

4. 1976

   A brief imperial year count

   Iran switches to an “imperial” era counted from Cyrus the Great, making 1355 SH the year 2535. The change is reversed in 1978.

5. Today

   Computed by astronomers

   Iran’s official calendar, including the moment of the new year, is prepared each year by the Calendar Center of the University of Tehran’s Institute of Geophysics.

Converting to the Gregorian calendar

A Persian year overlaps two Gregorian years: it starts around 20–21 March and ends the following March. That is why the year offset is 621 for most of the year but 622 between 1 January and Nowruz. For a side-by-side look at both calendars, read Persian vs Gregorian; to convert a specific date, use the converter.

Sources

1. Kazimierz M. Borkowski, “The Persian calendar for 3000 years”, Earth, Moon and Planets 74 (1996): 223–230. doi:10.1007/BF00055188
2. M. Heydari-Malayeri, “A concise review of the Iranian calendar” (2004). arXiv:astro-ph/0409620
3. Encyclopaedia Iranica, “Calendars”. iranicaonline.org/articles/calendars
4. MacTutor History of Mathematics, “Omar Khayyam”, University of St Andrews. mathshistory.st-andrews.ac.uk
5. “روند اصلاح تقویم هجری شمسی در ۱۳۰۴ش”, Journal of Historical Studies, University of Tehran. jihs.ut.ac.ir
6. “Shahanshahi calendar”, Wikipedia. en.wikipedia.org