In Iran and Afghanistan, the Solar Hijra calendar is used, also known as the Jalali Calendar.
- The months of Jalali calendar match the zodiac months.
- The years of the Jalali calendar match full rotations of the Earth around the Sun.
- Each of the four seasons of the year is roughly equivalent to three consecutive full months.
- The first day of the year in Jalali calendar, known as Nowrooz (21st of March), which is celebrated widely in the region, is the first day of "Farvardin" and the beginning of spring.
- The first six months are 31-day months and the next five months are 30-day months. The last month, Esfand, has 29 days. It becomes a 30-day month whenever it is a leap year (which happens roughly once in every four years).
- The names of the months in Iran have their roots back in Zoroastrian cosmology. The Dari month names used in Afghanistan are used only in astrological contexts in Iran.