How to Convert the Persian Calendar to a Christian Calendar

The Gregorian calendar is used in most of the western world.

The Persian calendar begins on the vernal equinox. It has 12 months, where the first six have 31 days, the next five have 30 days, and the last has either 29 or 30 depending on whether it's a leap year. The months in order are: Farvardin, Ordibehesht, Khordad, Tir, Mordad, Shahrivar, Mehr, Aban, Azar, Day, Bahman and Esfand. The modern Christian calendar is called the Gregorian calendar. It also has 12 months, where each month has between 28 and 31 days. It begins in the middle of winter and is not closely tied to a solar, lunar or seasonal cycle. Vernal equinox typically falls on March 21.

Instructions

1. Add 621 to the Persian year to arrive at the starting Gregorian year. For example, if the Persian year is 1389, the Gregorian year is 2010.

2. Count the number of days since the beginning of the year on the Persian calendar. For example, Farvardin 31 would be 31 days, and Tir 31 would be 124 days.

3. Find the precise point of time of the vernal equinox, determined astronomically, on the Gregorian calendar. The U.S. Naval Observatory's website has a chart of this data for the past 10 years. Select the date of the nearest midnight to it. For 2010, the time of the vernal equinox is March 20 at 5:32 p.m. The nearest midnight is on March 21.

4. Count the number of days between the vernal equinox date and January 1. For most years, there are 80 days.

5. Add the number of days between the vernal equinox and January 1 to the number of days since the beginning of the Persian calendar year. The result is the number of days since January 1 for the Gregorian calendar. For example, for Tir 31 1389, 80 + 124 is 204, which is July 23, 2010.

6. Subtract 365 (or 366 for Gregorian leap years) if the above result is more than 365 (or 366). This gives you the number of days since January 1 of the following year. For example, Bahman 1 1389 is the 307th day of the Persian calendar. Adding 80 results in 387, which is more than 365. Subtracting 365 results in 22 days since January 1, 2011, or January 22, 2011.

7. Repeat this process for each day of the Persian calendar until the whole thing has been converted into Gregorian.

References

• Frequently Asked Questions About Calendars 2.9: The Persian Calendar

Resources

• Iran Chamber Society: Iranian Calendar Converter
• U.S. Naval Observatory Astronomical Applications Department: Earth's Seasons
• NASA Goddard Earth Sciences Data and Information Services Center: Day of Year Calendar