به یاد باد صبا ˷ be yade bade saba

A documentary on the Persian poet, polymath, mathematician, philosopher, astronomer and physician - غیاث الدین ابو الفتح عمر بن ابراهیم خیام نیشاپوری  Omar Khayyám (1048 - 1131) from Neishapur in the province of Khorasan 

The modern Iranian Jalali calendar based on actual solar transit (year length of 365.2424 days) is based on Omar Khayyam’s calculations. The Jalali calendar requires an Ephemeris for calculating dates and has no seasonal error, since the length of each month may vary between 29 and 31 days depending on the moment when the sun crosses into a new zodiacal area.