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How to Convert Persian (Shamsi) Dates to Gregorian — Complete Guide

Published May 22, 2026 · Last updated May 2026

The Persian calendar, known as the Solar Hijri (شمسی / Shamsi) or Jalali calendar, is the official calendar of Iran and Afghanistan. With over 100 million people relying on it for daily life, business, and government records, the need to convert between Persian and Gregorian dates arises constantly — whether you are booking international flights, filing documents for immigration, scheduling cross-border meetings, or simply keeping track of birthdays and anniversaries across cultures.

This guide explains exactly how the two calendars differ, walks through the conversion logic step by step, provides a quick-reference table of month correspondences, and includes a free interactive converter tool you can use right now.

Why Date Conversion Between Shamsi and Gregorian Matters

Date conversion is not merely an academic exercise. It has practical implications in several real-world scenarios:

• International business: Contracts, invoices, and shipping documents between Iranian companies and their global partners require unambiguous dates. A delivery deadline of "15 Khordad 1405" means nothing to a warehouse in Rotterdam unless it is translated to "June 5, 2026."
• Immigration and legal records: Visa applications, birth certificates, marriage records, and academic transcripts issued in Iran use Shamsi dates. Embassies and foreign universities need Gregorian equivalents for processing.
• Travel planning: Iranian holidays like Nowruz (1 Farvardin), Sizdah Be-dar (13 Farvardin), or Yalda Night (30 Azar) need to be mapped to Gregorian dates so travelers can plan flights, book hotels, and understand business closure periods.
• Software development: Any application serving Iranian users — banking apps, e-commerce platforms, scheduling tools — must handle dual-calendar logic correctly. Bugs in date conversion can lead to missed payments, expired subscriptions, or scheduling errors.
• Personal record-keeping: Iranians living abroad often need to toggle between calendars for personal milestones, genealogy research, or communicating dates to family back home.

Fundamental Differences Between the Shamsi and Gregorian Calendars

The Shamsi and Gregorian calendars are both solar calendars — they track the Earth's orbit around the Sun. However, they differ in their epoch (starting point), month structures, and leap year rules.

Epoch

The Gregorian calendar counts years from the estimated birth of Jesus Christ. The year 2026 CE means 2,026 years after that epoch. The Shamsi calendar counts years from the Hijra — the Prophet Muhammad's migration from Mecca to Medina in 622 CE. However, unlike the Islamic lunar Hijri calendar, the Shamsi calendar is anchored to the vernal equinox (the first day of spring in the Northern Hemisphere). The current Shamsi year, 1405, began on March 20, 2026.

Month Lengths

Gregorian months follow an irregular pattern of 28–31 days with no clean structure. The Shamsi calendar is more orderly:

• The first 6 months (Farvardin through Shahrivar) each have 31 days.
• The next 5 months (Mehr through Bahman) each have 30 days.
• The final month (Esfand) has 29 days in a common year and 30 days in a leap year.

This adds up to 365 days in a common year (6×31 + 5×30 + 29 = 365) and 366 in a leap year — the same total as the Gregorian calendar, but distributed differently.

Leap Year Rules

The Gregorian leap year rule is well-known: a year is a leap year if it is divisible by 4, except for century years, which must be divisible by 400. This yields 97 leap years every 400 years, giving an average year length of 365.2425 days.

The Shamsi calendar uses a more precise but less intuitive system. It follows a 2,820-year grand cycle containing exactly 683 leap years. This produces an average year length of 365.24219858 days — astonishingly close to the actual tropical year of 365.24219 days. In practice, for the current era, leap years in the Shamsi calendar follow a pattern where 8 leap years are distributed across every 33-year sub-cycle, occurring at years 1, 5, 9, 13, 17, 22, 26, and 30 of each cycle.

Quick Reference: Shamsi Month Names and Gregorian Correspondence

The following table shows each Shamsi month, its length, and the approximate Gregorian date on which it begins. Because the Shamsi calendar is anchored to the vernal equinox, these start dates shift by at most one day depending on the year.

Common Conversion Examples

Here are some frequently needed conversions for the current Shamsi year, 1405:

Step-by-Step Conversion Logic (Conceptual)

Understanding the algorithm behind date conversion helps you trust the results and debug edge cases. Here is the conceptual process for converting a Shamsi date to Gregorian:

Step 1: Count Total Days from the Shamsi Epoch

Start from 1 Farvardin of year 1 in the Shamsi calendar (which corresponds to March 22, 622 CE in the proleptic Gregorian calendar). Calculate the total number of days elapsed up to your target Shamsi date by:

1. Counting the days in all complete years before the target year, accounting for leap years in each.
2. Adding the days in each complete month of the target year before the target month (using the 31/30/29 rule).
3. Adding the remaining days of the target month.

Step 2: Convert the Day Count to a Julian Day Number

A Julian Day Number (JDN) is a universal day-counting system used in astronomy and calendar conversions. By adding the known JDN of the Shamsi epoch to the day count from Step 1, you obtain the JDN of your target date.

Step 3: Convert the Julian Day Number to Gregorian

Standard formulas exist to convert a JDN into Gregorian year, month, and day. These formulas account for the Gregorian leap year rules and the varying month lengths. The result is your converted Gregorian date.

Reverse Direction (Gregorian to Shamsi)

The reverse conversion follows the same principle in the opposite order: convert the Gregorian date to a JDN, subtract the Shamsi epoch JDN to get the total day count, then decompose that count into Shamsi year, month, and day using the Shamsi month lengths and leap year pattern.

Try It Now: Interactive Shamsi ↔ Gregorian Converter

Use the tool below to convert dates instantly. No data is sent to any server — all calculations happen in your browser.

Important Tips and Edge Cases

Time Zone Awareness

The Shamsi calendar day starts at midnight Iran Standard Time (IRST, UTC+3:30). If you are converting dates for events that happen near midnight — or if you are in a different time zone — be aware that the Shamsi date might differ from what you expect. For example, an event at 11:00 PM on March 19 UTC is already March 20 in Iran, which is 1 Farvardin (Nowruz) if the equinox falls that year on March 20.

Leap Year Edge Cases

The last day of the Shamsi year is 29 Esfand in common years and 30 Esfand in leap years. When converting dates at the end of Esfand, always verify whether the Shamsi year in question is a leap year. Converting "30 Esfand" for a non-leap year is an invalid date and should produce an error. Shamsi years 1403 and 1408 are leap years; 1404, 1405, 1406, and 1407 are not.

Historical Dates

The modern Shamsi calendar was officially adopted in Iran in 1925 CE (1304 SH). For dates before this, conversions are mathematically valid but may not correspond to dates that were actually used in practice, since earlier eras used the Islamic lunar Hijri calendar or other systems.

Afghanistan Variations

Afghanistan uses the same Solar Hijri calendar but with different month names in Dari (e.g., Hamal instead of Farvardin, Sawr instead of Ordibehesht). The underlying calendar structure and conversion math are identical.

Use Boshkeh for Effortless Date Conversion

Boshkeh is a free utility app that includes a powerful date converter alongside other everyday tools. It handles Shamsi-to-Gregorian, Gregorian-to-Shamsi, and other calendar conversions with a clean, intuitive interface. Whether you need a quick conversion or want to explore how dates map across calendars, try Boshkeh's date converter — it works on any device, right in your browser.

Frequently Asked Questions

How do I convert a Persian date to Gregorian?

The mathematical approach involves computing the total number of days from the Shamsi epoch (1 Farvardin, year 1), converting that to a Julian Day Number, and then to a Gregorian date. In practice, use an online converter like the one on this page or Boshkeh's tool for instant results.

What Gregorian date is 1 Farvardin 1405?

1 Farvardin 1405 — Nowruz, the Persian New Year — falls on March 20, 2026 in the Gregorian calendar.

What is today's date in the Shamsi calendar?

Use the Gregorian → Shamsi converter above to convert today's date. You can also visit boshkeh.online/app/ for a live display of today's Shamsi date.

How do Persian leap years differ from Gregorian?

Persian leap years follow a complex 2,820-year cycle with 683 leap years, yielding an average year of 365.24219858 days. The Gregorian system uses a simpler 400-year cycle with 97 leap years (365.2425 days average). The Persian system is more astronomically precise.

Is there a free online Persian date converter?

Yes. You can use the interactive converter embedded on this page, or visit Boshkeh for a full-featured, free date conversion tool that works on all devices.