How to convert Shamsi to Gregorian dates and work out deadlines

Why you can't convert a Shamsi date by adding 621

The Persian calendar, also called Solar Hijri or Shamsi, is the official calendar in Iran and Afghanistan. Like the Gregorian calendar it follows the sun, but its year starts at the March equinox, on Nowruz. 1 Farvardin 1405 is March 21, 2026. One Persian year therefore covers parts of two Gregorian years: 1 Dey 1405 is December 22, 2026, and the rest of 1405 runs on into 2027.

Adding 621 to the year is right for most of 1405 and one year short for the weeks that fall in 2027, and the day of the month never carries over. These slips show up in documents that mix calendars, such as a contract between an Iranian company and a foreign partner, a visa form, or a birth date copied into a passport. Counting days across Persian months adds another trap, because the months are not all the same length.

Convert the date, count from it, then check the weekday

The Calendar Converter shows one day in five calendars at once: Gregorian, Persian, Islamic (Umm al-Qura), Hebrew, and Chinese. Choose Persian under From, enter the year, month, and day, and press Convert to get the Gregorian and ISO date. Going the other way, from a Gregorian date, the Persian date is listed first. It uses the calendar data built into your browser and supports Gregorian years 1000 to 9999.

For a deadline, take the Gregorian date into the Date Calculator and add the period. It adds or subtracts years, months, weeks, and days, and returns the new date with its weekday, ISO date, day of the year, and ISO week. Months are applied before days, and a month added to the 31st lands on the last day of a shorter month. Convert the result back to Persian in the Calendar Converter.

The weekday decides whether an office is open on the date you picked. Enter the Gregorian date in the Day of the Week Calculator to see it, along with the weekday of the same date in each of the next 10 years.