Iran's official calendar is the Solar Hejri calendar, beginning at the vernal equinox in the Northern Hemisphere, which was first enacted by the Iranian Parliament on 31 March 1925. Each of the 12 months of the Solar Hejri calendar correspond with a zodiac sign, and the length of each year is absolutely solar. The months are named after the ancient Iranian months, namely Farvardin (), Ordibehešt (), Xordād (), Tir (), Amordād (), Šahrivar (), Mehr (), Ābān (), Āzar (), Dey (), Bahman (), and Esfand ().