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 ocurred 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.
In the three calendars used by Zoroastrians it falls at different times in the Gregorian calendar: