The Iranian calendar (گاه‌شماری هجری خورشيدى) also known as Persian calendar or the Jalāli Calendar is a solar calendar currently used in Iran and Afghanistan. It is observation-based, rather than rule-based, beginning each year on the vernal equinox as precisely determined by astronomical observations from Tehran (or the 52.5°E meridian) and Kabul. This makes it more accurate than Gregorian calendar, but harder to work out which years are leap years.