Proleptic Julian calendar with year 0 corresponding to 1 BC, and "year −1" corresponding to 2 BC, so that in this system, Julian leap years have a number divisible by four. The determination of leap years in the proleptic Julian calendar (in either numbering) is distinct from the question of which years were historically considered leap years during the Roman era, due to the leap year error: Between 45 BC and AD 4, the leap day was somewhat unsystematic. Thus there is no simple way to find an equivalent in the proleptic Julian calendar of a date quoted using the Roman pre-Julian calendar
Zoroastrian calendar Zoroastrian Seasonal-Year Society. In 1906, the society published its proposal for a Zoroastrian calendar which was synchronised with the seasons. This "Fasli" calendar, as it became known, was based on the Jalali calendar introduced in 1079 during the reign of the Seljuk Malik Shah and which had been well received in agrarian communities. The Fasli proposal had two useful features: a leap-day once every four years, and harmony with the tropical year. The leap-day, called "Avardad-sal-Gah" (or in Pahlavi: "Ruzevahizak"), would be inserted, when required, after the five existing "Gatha" days at the end of the year. New Year's Day