Maidyoshahem (or Maidhyoishema in Avestan) is the gahambar, or Zoroastrian seasonal festival, of Hordad. Hordad is the Amesha Spenta, or Holy Immortal, who created water and is patron of wholeness and health. Maidyoshahem seems to have originally been a pre-historic midsummer festival. As with the other gahambar, it is a five-day festival — 11-15 Tir in the Zoroastrian calendar. Only in the Fasli calendar does Maidyoshahem fall in the summer.

The most important of the five days of Maidyosahem is the third day (13 Tir), which is Jashan-e Tiragan. Jasham-e Tiragan is a separate feast, but has become the main festival of Maidyoshahem. As Jashan-e Tiragan is dedicated to Tishtar, the yazad of the star Sirius and the pre-harvest rains, the festival links well with that of Hordad.

The current dates (according to the Gregorian calendar) for Maidyoshahem are:

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