Methodology and sources

The Persian (Solar Hijri) calendar

The Solar Hijri year begins at the moment of the March equinox, and its leap years follow from the same rule. This site calculates the leap years arithmetically, from 33-year cycles. The result has been compared with the official table of leap years of the Calendar Center of the Institute of Geophysics, University of Tehran, for the years 1206 to 1498, and every year matches. Conversion between the Persian and Gregorian calendars is exact.

The Islamic (lunar Hijri) calendar

In Iran, each Islamic month begins with the sighting of the new crescent and an official announcement, so tabular Islamic calendars sometimes differ from the official one by a day or two. This site takes the length of each month from Iran's official calendar: the start of every month since 1265 AH, from the public-domain qamari dataset (CC0), completed with the official calendar of 1405 up to the end of Ramadan 1448.

For months not yet officially announced, the date is estimated: a month begins on the evening when the moon is at least 18 hours old at sunset in Tehran. This rule has been tested on 1,166 past official months: 85 percent were exactly right and the rest only a day off. Each new official announcement, such as the start of Shawwal, is entered on the site and replaces the estimate.

Islamic dates in other countries, such as Iraq or Saudi Arabia, sometimes differ from Iran's by a day. The dates on this site follow Iran.

The Gregorian and Imperial calendars

Gregorian dates follow the Gregorian calendar. The Imperial (Shahanshahi) calendar, used in Iran from Esfand 1354 to Shahrivar 1357 (1976–1978), has the same months and days as the Solar Hijri calendar; only its year number is 1180 higher.

The moment of Nowruz

The moment of the March equinox is calculated from NASA's orbital data (JPL DE440) with the Skyfield library, and is within two seconds of the officially announced times. If the moment falls before noon in Tehran, that day is 1 Farvardin; if after, the next day is. Each city's local time, with daylight saving, comes from the IANA time zone database.

Prayer times

Prayer times follow the method of the Institute of Geophysics, University of Tehran, the method of Iran's official tables: fajr when the sun is 17.7° below the horizon, sunrise and sunset when the sun's upper edge meets the horizon (0.833° with refraction), dhuhr when the sun crosses the meridian, maghrib when the sun is 4.5° below the horizon, and the shar'i midnight halfway from sunset to fajr. The sun's position comes from the U.S. Naval Observatory's formulas; the times have been checked against NASA's orbital data (JPL DE440) and differ by less than ten seconds. Times are rounded to the minute. In cities where the sun does not get 17.7° below the horizon on summer nights, fajr is set before sunrise by the angle's share of the night (17.7 parts in 60). City coordinates come from GeoNames (CC BY 4.0).

Holidays and occasions

Each occasion is recorded as a rule in its own calendar: a day of a Persian month (such as 12 Farvardin), a day of an Islamic month (such as 10 Muharram), a Gregorian day, or a rule such as "the Tuesday before the last Wednesday of the year" for Chaharshanbe Suri. Each year's dates are built from these rules, so Islamic occasions fall in the right place in the Persian calendar every year. The 1405 holidays have been checked against that year's official calendar (26 days).

Each year's public holidays follow the law in force that year: the holiday circular of 1347 for 1347 to 1357 (1968–1979), and from 1358 the public holidays bill and the Act of Tir 1359 (1980) with its later amendments: the martyrdom of Imam Reza instead of his birthday (1377), the martyrdom of Fatima (1378), the second day of Eid al-Fitr (1390) and 8 Rabi al-Awwal (1396). 14 Khordad is shown as a holiday from its first anniversary, 1369, and 30 Esfand is a holiday in leap years. No list of public holidays is recorded for the years before 1347.

Newer occasions appear only from the year their event happened or they were named, and international days from the year they were first held. For days named in the official calendar after 1357 whose year of naming is unclear, 1358 is taken as the first year.

Some Iranian festivals, such as Mehregan and Tirgan, fall on different days under two calendar conventions; each festival's page (in Persian) explains both dates.

Names and translations

The English pages use the English names of the occasions and cities.

Report a mistake

If a date looks wrong, tell us through the contact form or at admin@persian-calendar.com.