Knowledge
The Persian Calendar Explained
A complete guide to understanding the Jalali Solar Hijri calendar — how it works, why it matters, and what makes it the most astronomically accurate calendar in widespread use.
What is the Persian Calendar?
The Persian calendar — officially called the Solar Hijri calendar, also known as the Jalali or Shamsi calendar — is the official civil calendar of Iran and Afghanistan. It is used daily by over 100 million people.
It is a solar calendar, meaning it is based entirely on Earth's orbit around the sun. The year begins precisely at the vernal equinox — the moment spring begins in the Northern Hemisphere. This is called Nowruz: "New Day."
The calendar consists of 12 months. The first six months have 31 days each; the next five have 30 days; and the last month (Esfand) has 29 days in a normal year and 30 days in a leap year.
How Does It Compare to the Gregorian Calendar?
The Gregorian calendar — the international standard — was introduced in 1582 CE to correct errors in the Julian calendar. It is extremely accurate, accumulating one day of error every 3,226 years.
The Persian calendar, reformed by Omar Khayyam in 1079 CE — 503 years before the Gregorian — is more accurate still: it accumulates one day of error every 3,770 years.
The key difference is in how leap years are calculated. The Gregorian system uses a simple but imprecise rule (every 4 years, except centuries, except 400-year multiples). The Jalali calendar uses a 2,820-year grand cycle with 683 leap years distributed in a pattern that precisely mirrors the astronomical solar year.
The Structure of the Year
The Persian year is divided into four seasons, each containing three months:
• Spring (Bahār): Farvardin, Ordibehesht, Khordad • Summer (Tābistān): Tir, Mordad, Shahrivar • Autumn (Pāiz): Mehr, Aban, Azar • Winter (Zemestān): Dey, Bahman, Esfand
Because the year begins at the spring equinox, the seasons align perfectly with the calendar months — always. There is never ambiguity about when a season begins.
The Month Names
The 12 Persian month names come from the ancient Zoroastrian religious tradition, specifically from the Avestan language — the sacred language of the Zoroastrian scriptures.
Each month is named for a Yazata (divine being) or Amesha Spenta (holy immortal) in Zoroastrian cosmology: Farvardin for the Fravashis (guardian spirits), Ordibehesht for Asha Vahishta (Best Truth), Mehr for Mithra (covenant and friendship), and so on.
These names have been in continuous use for over 2,500 years, making the Persian calendar one of the most linguistically ancient in current use.
The Persian Calendar for Farming & Nature
Because the Persian calendar begins at the spring equinox and its months align precisely with astronomical seasons, it is uniquely suited to agricultural and seasonal planning.
Farvardin 1 is always the first day of spring. Mehr 1 is always the first day of autumn. Dey 1 is always close to the winter solstice. This predictability means that farming guidance tied to Persian month numbers applies reliably every year — unlike Gregorian calendar months, which drift relative to the actual seasons.
This is why the Persian calendar was used for agricultural planning across the Iranian plateau for thousands of years.