The Solar Hijri calendar, also known as the Persian calendar, is a solar calendar used primarily in Iran and Afghanistan. It begins on the vernal equinox, marking the first day of spring, and consists of 12 months, totaling 365 days in a common year and 366 days in a leap year. The calendar is based on the Earth's revolutions around the Sun, making it highly accurate for seasonal changes. The Solar Hijri calendar is widely used for civil purposes in Iran, including official documents and holidays. Its months are named after natural phenomena and historical figures, with the first month being Farvardin. The calendar is also significant in cultural and religious contexts, influencing festivals like Nowruz, the Persian New Year.