Zoroastrian calendar

Adherents of Zoroastrianism use three distinct versions of traditional calendars for liturgical purposes, all derived from medieval Iranian calendars and ultimately based on the Babylonian calendar as used in the Achaemenid empire. Qadimi ("ancient") is a traditional reckoning introduced in 1006. Shahanshahi ("imperial") is a calendar reconstructed from the 10th century text Denkard.

Fasli is a term for a 1906 adaptation of the 11th century Jalali calendar following a proposal by Kharshedji Rustomji Cama made in the 1860s.

A number of Calendar eras are in use:

• A tradition of counting years from the birth of Zoroaster was reported from India in the 19th century. There was a dispute between factions variously preferring an era of 389 BCE, 538 BCE, or 637 BCE.
• The "Yazdegerdi era" (also Yazdegirdi) counts from the accession of the last Sassanid ruler, Yazdegerd III (16 June 632 CE). This convention was proposed by Cama in the 1860s but has since also been used in conjunctions with Qadimi or Shahanshahi reckoning. An alternative "Magian era" (era Magorum or Tarikh al-majus) was set at the date of Yazdegerd's death in 652.
• "Z.E.R." or "Zarathushtrian Religious Era" is a convention introduced in 1990 by the Zarathushtrian Assembly of California set at the vernal equinox (Nowruz) of 1738 BCE (−1737 in the astronomical year numbering).