The Iranian calendar, also known as the Persian calendar, is a solar calendar used in Iran and Afghanistan. It consists of 12 months, with the first month, Farvardin, beginning on the vernal equinox. The calendar is based on the Earth's revolutions around the Sun, making it more accurate than lunar calendars. Each year in the Iranian calendar has 365 days, with a leap year occurring every four years, adding an extra day to the last month, Esfand. The calendar is widely used for civil purposes and is important for cultural and religious events in Iranian society.