The Zoroastrian Calendar
The Calendars
Zoroastrianism has various calendars, including the Fasli, Shenshai/Shahanshahi, and Kadmi calendars. Although each calendar has differences, all share the trait that all days and months are named after either Ahura Mazda, the Amesha Spentas, or other holy divinities.
The Fasli Calendar
The Fasli calendar has alignment with the seasons and, similar to the Gregorian calendar, adds a leap day every 4 years. There are 12 months and 365 days in a year, with Nowruz always occurring on the vernal equinox.
The Shenshai Calendar
The Shenshai calendar is used and created by the Parsis in India. There are 12 months, or mahs, in a year and each month has 30 days, or rojs. Since there is a difference in the number of days in the Gregorian/Solar calendars (365 days) and the Shenshai calendar (360 days), festivals that relied on the sun were disrupted. Thus, the Parsis decided to add an extra month every 120 years. The Shenshai calendar explains why Parsi new year falls in August, while other Zoroastrians celebrate new year during March.
The Kadmi Calendar
The Kadmi calendar was used by the Zoroastrians in Iran and did not calculate an extra month like the Parsis did. A Zoroastrian priest from Iran visited India in the 1720s CE and noticed a discrepancy between the two calendars. The priests in India adjusted their Shenshai calendars to the Kadmi calendar as they believed the calendar from Iran should be more trusted/ was authentic (since it is from the "homeland).