How to use it
- Choose Gregorian date to Solar Hijri or Solar Hijri date to Gregorian in Convert.
- Type the Gregorian date, or the Solar Hijri year, Month and Day of the month.
- Read the Converted date, the Weekday and Nowruz of this year.
- Open Months of this Solar Hijri year to see the length of each month and the Gregorian day it starts on.
The Solar Hijri year and Nowruz
The Solar Hijri year is a solar year. It begins at the spring equinox, on 1 Farvardin (Nowruz), about 21 March in the Gregorian calendar. Its years are counted from the Hijra, as the Islamic calendar's are, so 1404 Solar Hijri is 2025 CE.
The first six months have 31 days, the next five have 30 days, and Esfand has 29 days in a common year and 30 in a leap year. Iran adopted this calendar by law of 31 March 1925.
How the leap years are found
The page uses the 33-year rule. A year is a leap year when the remainder of (25 × Y + 11) ÷ 33 is less than 8, which gives eight leap years in each 33 years. The rule reproduces the Nowruz dates that Wikipedia tabulates for the years 1368 to 1412 (1989 to 2033), with the leap years 1370, 1375, 1379, 1403, 1408 and 1412 marked there.
Iran's official calendar is set by the astronomical equinox, not by a formula, so the rule is an approximation: a Nowruz near the equinox can differ from the official day by one.
leap year when ((25 × Y + 11) mod 33) < 8What this converter does not cover
- Years outside 1300 to 1500, which the page does not convert. The checked range of the table is 1368 to 1412.
- The exact time of the equinox, which decides the day of Nowruz in the official calendar.
- Other Persian calendars, such as the Zoroastrian and the Iranian sidereal calendar that Iran used before 1925.
Worked example: 21 March 2025
Choose Gregorian date to Solar Hijri and keep the date 2025-03-21. The result is 1 Farvardin 1404, which is Nowruz, a Friday. The year 1404 is a common year, so it has 365 days and Esfand has 29.
Going the other way, choose Solar Hijri date to Gregorian and type 1403, month 12 and day 30. That gives 20 March 2025, the last day of the leap year 1403, one day before Nowruz 1404.
| Solar Hijri | Gregorian |
|---|---|
| 1 Farvardin 1404 | 21 March 2025 |
| 30 Esfand 1403 | 20 March 2025 |
Frequently asked questions
Is the Persian calendar the same as the Jalali calendar?
Yes, in practice. Jalali is the older name of the calendar, which a group of astronomers including Omar Khayyam drew up in the 11th century. The Solar Hijri calendar is the calendar of Iran since 1925, with the same months and the same first day, Nowruz.
Why does Nowruz fall on 20 or 21 March?
Nowruz is the day of the spring equinox in Tehran. That moment is about 21 March, and it can fall on 20 March, so the Gregorian date of Nowruz moves by a day from year to year.
Why is Esfand 29 days in some years and 30 in others?
Esfand has 30 days in a leap year and 29 in a common year. The 33-year rule decides which years are leap years, so that the Nowruz dates stay close to the equinox.
How exact is the 33-year rule?
It matches the Nowruz dates that Wikipedia lists for 1368 to 1412 (1989 to 2033). Outside those years a Nowruz can differ from the astronomical equinox by a day, so for an official date check the calendar of Iran.
Is the date I type sent to a server?
No. The calculation runs in your browser. Nothing you type is stored or sent to us, and you can use the page without an account.
Sources
- Wikipedia: Solar Hijri calendar (the 33-year table, the law of 1925, the Nowruz rule)
- Tøndering: Calendar FAQ, the Persian calendar (leap years and the 2820-year arithmetic)
Figures and text last checked on Tuesday, November 10, 2026.