Maidyoshahem

Maidyoshahem (Maidhyoishema; Mid-Summer Feast)

June-July, October-November, November-December; 11th-15th days of Tir, the fourth Zoroastrian month

This festival is the second of the six great seasonal festivals, known as gahambars, of the Zoroastrian religion. Each of the six gahambars correlates with a phase of agricultural production and honors one of the six things created by God: sky, water, earth, plants, animals, and humankind. Maidyoshahem was linked to the creation of the waters.
Traditionally, the gahambars were joyous festivals that lasted five days and provided farm workers with a much-needed respite from their labors. The first four days were spent in preparation for the feasting that took place on the fifth day. Today, however, so many Zoroastrians live in urban areas that the importance of the gahambars has diminished somewhat.
The Zoroastrian calendar has 12 months of 30 days each, plus five extra days at the end of the year. Because of discrepancies in the calendars used by widely separated Zoroastrian communities around the world, there are now three different calendars in use, and Maidyoshahem can fall either in June-July, October-November, or November-December, according to the Gregorian calendar.
See also Tiragan

SOURCES:
RelHolCal-2004, p. 67