Fasli refers to a specific version of the traditional calendars used by adherents of Zoroastrianism for liturgical purposes. While it is derived from medieval Iranian calendars and ultimately based on the Babylonian calendar used in the Achaemenid Empire, Fasli specifically represents a 1906 adaptation of the 11th-century Jalali calendar.
The development of the Fasli calendar followed a proposal made by Kharshedji Rustomji Cama during the 1860s. It exists alongside two other distinct versions: Qadimi (or Kadmi), which was introduced in 1006, and Shahanshahi, which is reconstructed from the 10th-century text Denkard.