Cappadocian calendar
The Cappadocian calendar was a solar calendar derived from the Persian Zoroastrian calendar. It is named after the historic region of Cappadocia in present-day Turkey, where it was used. The calendar, which had 12 months of 30 days each and five epagomenal days, originated between 550 and 330 BC, when Cappadocia was part of the Persian Achaemenid Empire. The Cappadocian calendar was identical to the Zoroastrian calendar; this can be seen in its structure, the Avestan names and the order of the months. The Cappadocian calendar reflects the influence of Iranian culture in the region. Extant evidence of the calendar dates back to Late Antiquity through the accounts of Greek astronomers, by which time it had already been adapted to the Julian calendar.
Context
The Cappadocian calendar was evidently devised when Cappadocia, a historical region in present-day Turkey, was a province (satrapy) of the Achaemenid Empire. The calendar is named after the region it was used in; there is no consensus about its precise starting date. According to the historian Josef Marquart, the calendar commenced in 490 BC, whereas according to the philologist Jacques Duchesne-Guillemin, it began between 490 and 480 BC. It is a solar calendar with 360 days divided into 12 months, which were followed by five epagomenal days.The calendar effectively imitated the Zoroastrian one; because the Persians were the dominant political group in Cappadocia then, it became the region's main calendar and survived as such in the Kingdom of Cappadocia. Although the passage of time and local dialect differences resulted in minor differences in spelling, the names of the months of the Cappadocian calendar are almost identical to those of the Zoroastrian calendar. The Persians in Cappadocia spoke western Iranian; therefore, the Cappadocian month-names are in some aspects linguistically closer to Middle Persian spelling rather than Avestan spelling. The Cappadocian forms, however, are more archaic and are closer in this regard to the Avestan forms.
The Cappadocian calendar is evidence of the long-lasting Iranian cultural and religious influences on Cappadocia. According to the Iranologist Mary Boyce, the Cappadocian calendar, together with the Middle Persian, Parthian, Sogdian, Khwarazmian, Bactrian, and Old Armenian calendars, were all derived from the Achaemenian state calendar that the Persians had introduced in the early Achaemenid period to establish the "accepted means of time-reckoning for all their Zoroastrian subjects". Over time, local language changes resulted in different local versions. Other than that, these calendars are almost identical. The Cappadocian calendar survived through the texts of Greek astronomers of Late Antiquity and was still known as late as the 4th century AD.