The day is divided into 5 watches or parts called GEHS. They are Havan Geh from Sunrise to Noon. Rapithvan Geh from Noon to 3:40 pm, Uziran Geh from 3:40 pm to Sunset. Aiwisruthrem Geh from Sunset to Midnight and Ushen Geh from Midnight to Dawn. The Period between dwan and midnight is called the Hojbarn period.

A month consists of 30 days named after Ahura Mazda, sthe 6 Arch Angels and Angels. There are 12 such months named after the Arch Angels. The last five days of the year are named after the 5 Holy Gathas. This makes 365 days in the year. There is no leap year but  a whole month was added every 120 years. This is inadvertently not been done since the reign of the last Iranian King, who was overthrown by the Arabs. A few people who were in  contact with the king added the one month, while the rest of the people in Iran forgot to do so. This has led to there being two calendars with a gap of one month between them. About 100 years ago a scholar Mr. K.R. Cama suggested a correction by starting the year on 21st March (the original New Year) and adding a day every leap year. Some people are following this calendar also.

Our calendar starts from the time of the coronation of the last Zoroastrian monarch of Iran around AD 630. Hence AD 1996 becomes YZ 1366.