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Notes on time, calendars, and dates: how the Persian (Jalali / Shamsi) and Gregorian systems work, where they disagree, and how to convert between them with confidence.
All postsهمه نوشتهها
- Nowruzنوروز
When is Chaharshanbe Suri? Working out the date each year
It is the eve of the last Wednesday of the Persian year, not simply the last Tuesday before Nowruz — and in 1402 those two rules were a week apart.
- Date mathحساب تاریخ
Iran's fiscal year: the exact start and end dates
It runs 1 Farvardin to the end of Esfand — but the common "21 March to 20 March" shorthand is wrong in over a third of years.
- Calendarsتقویمها
Is the date on your Afghan document solar or lunar?
A bare year of 1385 could mean 2006 or 1965 — a 41-year difference. How to tell solar Hijri from lunar Hijri from the month name.
- Calendarsتقویمها
Reading Persian numerals on a date: ۱۴۰۵ and the other nine digits
The Persian digit set, the four glyphs that differ from Arabic, why digits read left to right inside right-to-left text, and how to check your reading.
- Date mathحساب تاریخ
Shamsi dates in Excel and Sheets (and the formula that gets 29% wrong)
Why formatting a cell to a Persian calendar changes nothing, and why the most-copied conversion formula is a day off for most older birth dates.
- Calendar historyتاریخ تقویم
Why an Iranian document says 2535: the Imperial calendar
A birth certificate dated 2535 is not a typo. Subtract 1180 to get the Shamsi year — and only 2535 to 2537 appear on genuine documents.
- Calendarsتقویمها
Afghan month names: Hamal to Hut, and their Iranian equivalents
Hamal, Sawr, Mizan and the rest, mapped to Farvardin, Ordibehesht and Mehr — plus why the +621 shortcut gets the last three months wrong.
- Calendar referenceمرجع تقویم
How the Persian (Solar Hijri) calendar works
A complete, plain-English guide to the Persian calendar: the solar year, the 12 months, the 33-year leap cycle, the era count, and how it maps to Gregorian.
- Calendar referenceمرجع تقویم
Why the Persian year starts at the spring equinox
The Persian year begins at the vernal equinox, not 1 January. Why it is tied to an astronomical event, and how that keeps the calendar accurate.
- Nowruzنوروز
When is Nowruz in your timezone?
Nowruz happens at a single global instant, the spring equinox, so its clock time differs by timezone. How to find the exact moment where you are.
- Date mathحساب تاریخ
What day of the week was I born?
Find the weekday you were born on, why it is the same in the Persian and Gregorian calendars, and what that day is called in Persian.
- Nowruzنوروز
Nowruz 2027: date, time, and countdown
Nowruz 2027 falls on Sunday 21 March 2027, starting the Persian year 1406. The exact date, why it is the 21st, and a live countdown to the day.
- Calendar referenceمرجع تقویم
Farvardin: the first month of the Persian calendar
Farvardin is the first month of the Persian (Shamsi) year, starting at Nowruz. Its 31 days, the Gregorian dates it covers, and where it sits in the year.
- Calendarsتقویمها
Convert Jalali to Gregorian in code (JS & Python)
How to convert Jalali (Shamsi) dates to Gregorian in JavaScript and Python, which libraries to use, and the edge cases to test so your conversions stay correct.
- Leap yearsسالهای کبیسه
30 Esfand: the day that only exists in leap years
Why 30 Esfand appears only in Persian leap years, how it mirrors 29 February, and how to tell whether a 30 Esfand date is valid for a given year.
- Calendarsتقویمها
Shamsi and Gregorian conversion, explained
A complete guide to converting between the Persian (Shamsi / Jalali) and Gregorian (Miladi) calendars: the year offset, month lengths, leap years, and pitfalls.
- Nowruzنوروز
What is Nowruz? Dates, the equinox, and traditions
Nowruz is the Persian New Year, marking the spring equinox on 20 or 21 March. What it is, why the date moves, and the traditions like the haft-sin table.
- Age & birthdaysسن و تولد
How old am I in the Persian calendar?
Work out your age in the Persian (Shamsi) calendar, why it can differ by a year from your Gregorian age, and how to get the exact number in seconds.
- Calendarsتقویمها
Gregorian to Shamsi: convert any date the easy way
How to convert a Gregorian (Miladi) date to the Persian (Shamsi / Jalali) calendar, the quick rule for the year, and why converting beats doing it by hand.
- Two calendarsدو تقویم
Is the Persian calendar lunar or solar?
The Persian (Shamsi) calendar is solar, tied to the spring equinox, not lunar. Here is how it differs from the lunar Islamic (Hijri) calendar.
- Calendarsتقویمها
What year is it in the Persian calendar right now?
The current Persian (Shamsi) year is 1405, rolling to 1406 at Nowruz. Here is why it is ~621 years behind the Gregorian year, and how to convert any year.
- Calendarsتقویمها
Today's date in the Persian (Shamsi) calendar
What today is in the Persian (Shamsi / Jalali) calendar, how to read it, and how to convert any Gregorian date to the Iranian calendar in one step.
- Two calendarsدو تقویم
Gregorian vs Solar Hijri: two calendars on one timeline
How the Gregorian and Solar Hijri (Jalali) calendars line up: the ~621 year offset, the new-year gap, and a side-by-side table for recent years.
- Leap yearsسالهای کبیسه
What is a leap year? The 4 / 100 / 400 rule explained
A leap year has 366 days, with 29 February added to keep the calendar in sync with the Sun. Here is the 4/100/400 rule, why it exists, and a checker.
- Age & birthdaysسن و تولد
How old am I exactly? Age in years, months, and days
Your exact age in years, months, and days, not just the year count. Enter your birth date below, plus the method and why month lengths make it tricky.
- Calendar referenceمرجع تقویم
Persian (Jalali) calendar months in order, with meanings
The 12 Persian (Jalali / Shamsi) months in order, their lengths, the Gregorian dates each one covers, and what each name means, in one reference table.
- Calendar historyتاریخ تقویم
Why does February have 28 days (and sometimes 29)?
February is short because of Roman calendar politics, and it gains a 29th day on leap years. Here is the history and the rule, with a leap-year checker.
- Date mathحساب تاریخ
How to calculate the number of days between two dates
Count the days between two dates by hand or with a calculator. The method, a worked example, the leap-year gotcha, and a live tool that does it instantly.
- Nowruzنوروز
Why Nowruz isn't always on the same Gregorian day
Nowruz tracks the spring equinox, so on the Gregorian calendar it lands on 20 or 21 March depending on the year. Here is why the date drifts, with a table.
- Leap yearsسالهای کبیسه
Persian (Jalali) leap years, explained
How leap years work in the Persian (Jalali / Solar Hijri) calendar, why the extra day is 30 Esfand, and the 33-year cycle behind the rule.