Mehregan

Mehregān ( or Jašn-e Mehr "Mithra Festival") is a Zoroastrian and Persian festival celebrated to honor the yazata Mithra (), which is responsible for friendship, affection and love. It is also widely referred to as the Persian Festival of Autumn.
Introduction.
According to "The Wiley-Blackwell Companion to Zoroastrianism" (2015), it was originally a feast honoring the Zoroastrian "yazata" Mithra. By the 4th century BCE, it was observed as one of the name-day feasts, a form it retains in today. Still, in a predominantly Muslim Iran, it is one of the two pre-Islamic festivals that continue to be celebrated by the public at large: Mehrgān, dedicated to Mithra (modern "Mehr"), and Tirgan, dedicated to Tishtrya (modern "Tir").
Name-day feasts are festivals celebrated on the day of the year when the day-name and month-name dedicated to a particular divinity intersect. The Mehr day in the Mehr month corresponded to the day farmers harvested their crops. They thus also celebrated the fact Ahura Mazda had given them food to survive the coming cold months.
Irrespective of which calendar is observed, Mehrgān falls on the 196th day of the calendar year. For details on how this date is calculated, see basis for the date, below. For calendars that have March 21 as Nowruz or New Year's Day (i.e. in the "Fasili" and "Bastani" variants of the Zoroastrian calendar as well as in the Iranian civil calendar), Mehrgān falls on October 2. For the "Shahanshahi" variant of the Zoroastrian calendar, which in 2006–2007 has New Year's Day on August 20, Mehrgān fell on March 3 of the following Gregorian year. For the "Kadmi" variant, which has New Year's Day 30 days earlier, Mehrgān falls on February 1.
In al-Biruni's eleventh-century "Book of Instructions in the Elements of the Art of Astrology" (233), the astronomer observed that "some people have given the preference to Mihragān [over Nowruz, i.e. New Year's day/Spring Equinox] by as much as they prefer autumn to spring."
As Biruni also does for the other festival days he mentions, he reiterates a local anecdotal association for his description of Mehrgan ("ha al-mirjan" in the author's Arabic parlance) with a fragment of a tale from Iranian folklore: On this day, Fereydun vanquished the evil Zahhak and confined him to Mount Damavand. This fragment of the legend is part of a greater cycle that ties Mehrgan with Nowruz; Dahak vanquished Jamshid (who the legends have as the one establishing Nowruz or New Year's Day), and Fereydun vanquishes Dahak, so restoring the balance. The association of Mehrgan with the polarity of spring/autumn, sowing/harvest and the birth/rebirth cycle did not escape Biruni either, for as he noted, "they consider Mihragān as a sign of resurrection and the end of the world, because at Mihragān that which grows reaches perfection."
In ancient times.
Mehrgān was celebrated in an extravagant style at Persepolis. Not only was it the time for harvest, but it was also the time when the taxes were collected. Visitors from different parts of the Persian Empire brought gifts for the king all contributing to a lively festival.
During pre-Islamic and early Islamic Iran, Mehrgān was celebrated with the same magnificence and pageantry as Nowruz. It was customary for people to send or give their king, and each other, gifts. Rich people usually gave gold and silver coins, heroes and warriors gave horses while others gave gifts according to their financial power and ability, even as simple as an apple. Those fortunate enough would help the poor with gifts.
Gifts to the royal court of over ten thousand gold coins were registered. If the gift-giver needed money at a later time, the court would then return twice the gift amount. Kings gave two audiences a year: one audience at Nowruz and other at Mehregān. During the Mehregān celebrations, the king wore a fur robe and gave away all his summer clothes.
After the Mongol invasion of Iran, the feast celebration of Mehrgān lost its popularity. Zoroastrians of Yazd and Kermān continued to celebrate Mehrgān in an extravagant way.
In the present-day.
For this celebration, the participants wear new clothes and set a decorative, colorful table. The sides of the tablecloth are decorated with dry marjoram. A copy of the Khordeh Avesta ("little Avesta"), a mirror and a "sormeh-dan" (a traditional eyeliner or kohl) 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" (seeds of "Peganum harmala", Syrian rue) to be thrown on the flames.
At lunch time when the ceremony begins, everyone in the family stands in front of the mirror to pray. Sharbat is drunk and then—as a good omen—"sormeh" is applied around the eyes. Handfuls of wild marjoram, lotus and sugar plum seeds are thrown over one another's heads while they embrace one another.
In 1960s the Postal Service in Tehran issued a series of stamps to commemorate Mehrgan Festival.
Basis for the date.
As noted above, Mehrgān is a name-day feast. These name-day feasts are festivals celebrated on the day of the year when the day-name and month-name dedicated to a particular angel or virtue intersect. Indeed, Zoroastrian Persians before Islam had 30-days months, which means that each day in a month had a different name, with 12 of the days also being names of the 12 months. The day whose name corresponded to the name of the month was celebrated. It was a celebration of life, seasons changing, God, and joy. In Zoroastrianism, happiness is very important and is considered as a holy virtue that must be attracted. Thus, this religion has always had many feasts and celebrations.
What that day corresponds to in another calendar is subject to which variant of the Zoroastrian calendar is followed:
The "Bastani" calendar is used primarily in Greater Iran and by Persians of the diaspora, while Zoroastrians of India (subject to calendrical faction) use one of the other three variants.
Non-Zoroastrian Iranians do not observe any variant of the Zoroastrian calendar, but instead use Iranian calendars. When introduced in 1925, the Zoroastrian festival days were pegged to the "Bastani" variant of the Zoroastrian calendar. The first six months of the civil calendar had 31 days each, while all Zoroastrian calendar months have 30 days each. So by the 7th month (Mehr) there is a difference of 6 days between the two. Thus, October 8, which in the "Bastani"/"Fasili" calendar is the 16th day of Mehr month, is in the Persian civil calendar the 10th day (Aban) of Mehr.
The relationship between Mehregān and the various calendars is perhaps better understood relative to Nowruz. When (relative to another calendar) the first day of the year occurs is subject to interpretation, but independent of when it occurs, Mehregān is celebrated 195 days after that, that is on the 196th day of the year.
Notes.
http://Mehrgan.nipoc.org/