Why Nowruz isn't always on the same Gregorian day

Every year Nowruz, the Persian New Year, falls on 1 Farvardin, the first day of the Persian (Jalali / Solar Hijri) calendar. That part never changes. Yet if you look it up on a Gregorian (Miladi) calendar, the date moves: some years it is 20 March, other years it is 21 March. People often assume one of those is “wrong,” but both are correct. The drift is built into how the two calendars are defined.

Nowruz is an astronomical event, not a fixed date

The Persian calendar is tied to the March (vernal) equinox, the moment the Sun crosses the celestial equator and day and night are roughly equal. The new year begins on the day that contains that exact instant, observed at the reference meridian for Iran Standard Time. The equinox is an astronomical event, and it does not happen at the same clock time every year.

A tropical year, one full cycle of the seasons, is about 365.2422 days, not a whole number (source: timeanddate.com, March equinox). So the equinox arrives almost six hours later each year, then jumps back by roughly a day whenever a leap day is inserted. Because the Persian calendar pins 1 Farvardin to the equinox, Nowruz tracks that astronomical drift directly. The Gregorian calendar, meanwhile, uses its own fixed leap rule (divisible by 4, with the century exceptions). The two systems absorb that fractional ⅕-of-a-day differently, so the Gregorian label on Nowruz shifts between 20 and 21 March.

Recent and upcoming dates

Here is 1 Farvardin mapped to its Gregorian date for a span of years, computed with the same engine the converter uses:

Notice the pattern: the date tends to fall back to 20 March in or just after a Persian leap year, then settle on 21 March for the next few years before drifting back again. For example, Nowruz 1403 fell on 20 March 2024 (a leap year), then 1404 and 1405 sat on 21 March. It is the same mechanism that puts 29 February on the Gregorian calendar every four years, just measured from the other side.

Why this matters when you convert dates

If you are converting a birthday, an anniversary, or a historical event around late March, the day-of-month genuinely depends on the year. Hard-coding “Nowruz = 21 March” will be off by a day in roughly a quarter of years. The safe approach is to convert each specific date rather than rely on a remembered rule, which is exactly what a calendar converter is for.

Want the mechanics of the leap rule itself? Read Persian (Jalali) leap years, explained, see how long until the next one in days until Nowruz, or jump straight to the Jalali ⇄ Gregorian converter to check any date.