Which Persian-language calendar uses the vernal equinox to anchor its New Year?

The Solar Hijri calendar uses the vernal equinox to anchor its New Year.

The Solar Hijri calendar is the official calendar of Iran and Afghanistan, with regional naming differences. Its year begins at Nowruz, whose precise starting moment is tied to the astronomical vernal equinox. As a result, the first day of the calendar can fall on March 20 or March 21 in the Gregorian calendar, depending on the equinox and the local calendar rule.

The calendar counts years from the Hijra, the migration of Muhammad from Mecca to Medina, but it is solar rather than lunar. Its months track the seasons, making it different from the Lunar Hijri calendar used for Islamic religious dates, which moves through the Gregorian seasons.

The Solar Hijri calendar is also called the Persian calendar in many contexts. It should not be confused with the historical Jalali calendar, the calendar reform associated with Omar Khayyam and other scholars, or with the Gregorian calendar used internationally.