There are three calendars of ancient Iran: the Old Avestan, Young Avestan and Old Persian calendars.
Gathic people were aware of the lunar year as well as the solar and settled five important turns of season on the ecliptic while they made them adjust the solar vague year. It is probable that even a Metonic cycle was known to some extent.
The young Avestan and the Old Persian calendars are the complex of the solar, lunar and lunisolar calendars.
Problems of months of the beginning of the year, the five-day stolen month and the ten-day fravardigan at the end of the year, the Zoroastrian weeks, and the Hamaspathmaedaya feast are illustrated.
