Persian Calendar Converter
Convert between Gregorian, Hijri, and the Persian Solar Hijri (Jalali) calendar. Enter values for instant results with step-by-step formulas.
Formula
JDN = day + floor((153m+2)/5) + 365y + floor(y/4) - floor(y/100) + floor(y/400) - 32045
The Julian Day Number (JDN) serves as an intermediary for calendar conversions. Each calendar system has algorithms to convert to and from JDN, enabling accurate date translation between Persian, Gregorian, and Hijri calendars.
Worked Examples
Example 1: Converting March 21, 2026 to Persian Calendar
Problem: Convert the Gregorian date March 21, 2026 to the Persian (Jalali) and Hijri calendars.
Solution: Using the Julian Day Number algorithm:\nJDN for March 21, 2026 = 2,461,826\nPersian epoch JDN = 1,948,321\nDays since epoch = 513,505\nUsing the 2820-year cycle algorithm:\nPersian date = 1 Farvardin 1405\nFor Hijri: JDN - 1,948,440 + 10632 = Hijri calculation\nHijri date = 22 Shaban 1447
Result: Gregorian: March 21, 2026 | Persian: 1 Farvardin 1405 | Hijri: 22 Shaban 1447
Example 2: Converting Persian Date 1 Mehr 1404 to Gregorian
Problem: Convert the Persian date 1 Mehr 1404 (first day of autumn in Persian calendar) to Gregorian.
Solution: 1 Mehr is the 187th day of the Persian year (6 months of 31 days + 1 day)\nPersian year 1404, month 7, day 1\nUsing the reverse algorithm through JDN:\nJDN = Persian epoch + yearly offset + day of year\nConverting JDN back to Gregorian gives September 23, 2025
Result: Persian: 1 Mehr 1404 | Gregorian: September 23, 2025 (Autumn Equinox)
Frequently Asked Questions
What is the Persian (Jalali) calendar and how does it differ from the Gregorian calendar?
The Persian calendar, also known as the Solar Hijri or Jalali calendar, is a solar calendar used officially in Iran and Afghanistan. It was reformed by Omar Khayyam and other astronomers in 1079 CE. Unlike the Gregorian calendar which starts from the estimated birth of Jesus, the Persian calendar counts years from the migration (Hijra) of Prophet Muhammad in 622 CE but uses solar year calculations rather than lunar. The first six months have 31 days each, the next five have 30 days, and the last month has 29 days (or 30 in leap years). The Persian New Year, Nowruz, falls on the vernal equinox around March 20-21, making it astronomically precise.
How accurate is the Persian calendar compared to the Gregorian and Hijri calendars?
The Persian calendar is considered one of the most accurate calendars ever devised. It has an error of only one day in approximately 3.8 million years, compared to the Gregorian calendar which accumulates an error of one day every 3,236 years. This remarkable accuracy comes from its leap year algorithm which uses a 2820-year grand cycle. The Hijri (Islamic) calendar, being purely lunar with 354 or 355 days per year, drifts approximately 11 days each year relative to the solar year, completing a full cycle through all seasons every 33 years. The Persian calendar stays perfectly aligned with the seasons because it is anchored to the vernal equinox.
What are the months and seasons of the Persian calendar?
The Persian calendar has twelve months organized into three groups reflecting the seasons. Spring months are Farvardin (31 days), Ordibehesht (31 days), and Khordad (31 days). Summer months are Tir (31 days), Mordad (31 days), and Shahrivar (31 days). Autumn months are Mehr (30 days), Aban (30 days), and Azar (30 days). Winter months are Dey (30 days), Bahman (30 days), and Esfand (29 or 30 days). The first day of Farvardin always coincides with the spring equinox, making the calendar naturally aligned with the astronomical seasons without any need for artificial adjustments.
How does the Hijri (Islamic) calendar conversion work?
The Hijri calendar is a purely lunar calendar consisting of 12 months that alternate between 29 and 30 days, resulting in a year of 354 or 355 days. Conversion between Gregorian and Hijri dates requires algorithms based on the Julian Day Number system, which provides a continuous count of days since January 1, 4713 BCE. The Hijri epoch corresponds to July 16, 622 CE in the Julian calendar. Because the Hijri year is about 11 days shorter than the solar year, Islamic dates cycle through all Gregorian seasons over a period of approximately 33 years. Important Islamic dates like Ramadan occur at different Gregorian dates each year.
What is the difference between business days and calendar days?
Calendar days include every day. Business days (or working days) exclude weekends (Saturday and Sunday) and public holidays. A 10-business-day deadline is typically 14 calendar days. Legal and financial deadlines often specify which type applies.
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