An Etymological Dictionary of Astronomy and Astrophysics

An Iranian solar calendar, based on two successive passages of the Sun through the true → vernal equinox. It results from a reform undertaken by a group of astronomers led by Omar Khayyam (A.D. 1048-1131). The current → Iranian calendar is an improved version of the Jalali calendar.

See also: Jalali, from the name of the ruler Jalâleddin Malek Šâh
of the Saljuqid dynasty, who ordered the reform; → calendar.