Maidyarem (or Maidhyairya in Avestan) is the ancient Iranian mid-winter festival. It is a gahambar, one of six major, seasonal, five-day festivals in Zoroastrianism. Originally, it would have occurred at the time of the winter solstice. However, many Zoroastrians and Parsis observe it in May or June, due to confusion over the ancient calendar.
Theologically, Maidyarem is associated with Vahman, the Amesha Spenta (or Holy Immortal) who created the primal bull, and all cattle, and is associated with good plans and intentions.
Maidyarem is celebrated in Dey, the tenth month of the Zoroastrian calendar, from the sixteenth (Mihr) to the twentieth (Bahram) day.
In the three calendars used by Zoroastrians it falls at different times in the Gregorian calendar: