Mehregan, one of the most ancient Iranian festivals known, dates back at least as far as the earliest Aryans (Iranians). 

Widely referred to as Persian festival of autumn, this time-honored event is celebrated in respect for Mithra, the divinity of covenant which according to ancient Iranian belief was responsible for friendship, affection and love.

The event falls on the sixteenth day of the seventh Iranian month in accordance to the Zoroastrian religious calendar. 

To setup, Participants wear new clothes and set a decorative, colorful table for celebrating Mehregan. 

The sides of the tablecloth are decorated with dry wild marjoram. A copy of Khordeh Avesta (Little Avesta), a mirror and a sormeh dan (an antimony container) are placed on the table together with rosewater, sweets, flowers, vegetables and fruits, especially pomegranates and apples, and nuts such as almonds or pistachios. 

A few silver coins and lotus seeds are placed in a dish of water scented with marjoram extract. 

A burner is also part of the table setting for kondor/loban (frankincense) and espand (Syrian rue seeds) to be thrown on the flames. 

At lunch time, everyone in the family stands in front of the mirror to pray. A cool fruit drink is served and then--as a good omen--antimony is rubbed around the eyes. Handfuls of wild marjoram, lotus and sugar plum seeds are thrown over each other’s heads while they embrace one another. 

There are many accounts about the origin of Mehregan. Avestan texts divide the Iranian year into two equal parts or seasons; summer and winter.

The advent of the two seasons would be celebrated through Norouz and Mehregan. 

It was celebrated on the 16th of the seventh Iranian month, Mehr, at the time of harvest and beginning of winter. This feast would be celebrated for six days, starting on the 16th (Mehr Rouz) and ending on the 21st (Raam Rouz). 

The first day was called Mehregan-e Khord and the last day Mehregan-e Bozorg. On these days, farmers carried out their harvest and prayed to God for it. 

The ancient Iranian calendar had 12 months and each month contained 30 days. 

Since, in the new Iranian calendar, the first six months of the year have 31 days, Mehregan arrives six days earlier, i.e. 10th of Mehr. 

During Achaemenid era (c. 550–330 BCE), Mehregan was celebrated in an extravagant style at Persepolis. It was both the time for harvest and time when the taxes were collected. 

Visitors from different parts of the empire brought gifts for the king, which contributed to a lively festival. 

During pre-Islamic and early Islamic Iran, Mehregan was celebrated with the same magnificence and pageantry as Norouz. It was customary for people to give gifts to the king. Rich people usually gave gold and silver coins, heroes and warriors gave horses while others gave gifts according to their ability, even fruits. 

According to the Iranian mythology, Fereydoun’s victory over Azydahak (Zahhak in Ferdowsi’s Shahnameh) happened on this day. Hence, Mehregan is a day of victory when angels helped Fereydoun and Kaveh gain victory over Zahhak. They managed to imprison him in the Damavand Mountain where he died from his wounds six days later. 

In Al-Biruni’s 11th-century book of instructions on the art of astrology, the astronomer observed that some people gave preference to Mehregan over Norouz just as they prefer autumn over spring.