Iranian calendars

The Iranian calendars also called Persian calendars (Persian: Taqwime Fārsi‎ Gāhŝomāriye Irāni) are a succession of calendars invented or used for over two millennia in Greater Iran. One of the longest chronological records in human history, the Iranian calendar has been modified time and again during its history to suit administrative, climatic, and religious purposes.
The modern Iranian calendar (Solar Hijri calendar (SH)) is now the official calendar in Iran and Afghanistan. It begins on the vernal equinox as determined by astronomical calculations for the Iran Standard Time meridian (52.5°E or GMT+3.5h). This determination of starting moment is more accurate than the Gregorian calendar as far as predicting the date of the vernal equinox is concerned because it uses astronomical calculation rather than mathematical rules.[1] but requires consulting an astronomical almanac.
Its years are designated AP, short for Anno Persico. The Iranian year usually begins within a day of 21 March of the Gregorian calendar. To find the corresponding year of the Gregorian calendar, add 621 or 622 (depending on the time of the year) to a Solar Hijri year. A short table of year correspondences between the Persian and Gregorian calendars is provided below.

Ancient calendars
Although the earliest evidence of Iranian calendrical traditions is from the second millennium BC, predating the appearance of the Iranian prophet Zoroaster, the first fully preserved calendar is that of the Achaemenids. Throughout recorded history, Persians have been keen on the idea and importance of having a calendar. They were among the first cultures to use a solar calendar and have long favoured a solar over lunar and lunisolar approaches. The sun has always been a symbol in Iranian culture and is closely related to the folklore regarding Cyrus the Great himself.

Old Persian calendar

Old Persian inscriptions and tablets indicate that early Iranians used a 360-day calendar based on the Babylonian system (the Babylonian Calendar was lunar) and modified for their beliefs. Days were not named. The months had two or three divisions depending on the phase of the moon. Twelve months of 30 days were named for festivals or activities of the pastoral year. A 13th month was added every six years to keep the calendar synchronized with the seasons.
The following table lists the Old Persian months.

Zoroastrian calendar

Main article: Zoroastrian calendar
The first calendars based on Zoroastrian cosmology appeared in the later Achaemenid period (650 to 330 BCE). They evolved over the centuries, but month names changed little until now.
The unified Achaemenid empire required a distinctive Iranian calendar, and one was devised in Egyptian tradition, with 12 months of 30 days, each dedicated to a yazata (Eyzad), and four divisions resembling the Semitic week. Four days per month were dedicated to Ahura Mazda and seven were named after the six Amesha Spentas. Thirteen days were named after Fire, Water, Sun, Moon, Tiri and Geush Urvan (the soul of all animals), Mithra, Sraosha (Soroush, yazata of prayer), Rashnu (the Judge), Fravashi, Bahram (yazata of victory), Raman[disambiguation needed] (Ramesh meaning peace), and Vata, the divinity of the wind. Three were dedicated to the female divinities, Daena (yazata of religion and personified conscious), Ashi (yazata of fortune) and Arshtat (justice). The remaining four were dedicated to Asman (lord of sky or Heaven), Zam (earth), Manthra Spenta (the Bounteous Sacred Word) and Anaghra Raocha (the 'Endless Light' of paradise).
The month names and their modern versions are given in the following table.

The calendar had a significant impact on religious observance. It fixed the pantheon of major divinities, and also ensured that their names were uttered often, since at every Zoroastrian act of worship the yazatas of both day and month were invoked. It also clarified the pattern of festivities; for example, Mitrakanna or Mehregan was celebrated on Mithra day of Mithra month, and the Tiri festival (Tiragan) was celebrated on Tiri day of the Tiri month.
After the conquests by Alexander of Macedon and his death, the Persian territories fell to one of his generals, Seleucus (312 BCE), starting the Seleucid dynasty of Iran. Based on the Greek tradition, Seleucids introduced the practice of dating by era rather than by the reign of individual kings. Their era became known as that of Alexander, or later the Seleucid era. Since the new rulers were not Zoroastrians, Zoroastrian priests lost their function at the royal courts, and so resented the Seleucids. Although they began dating by eras, they established their own era of Zoroaster.
That was the first serious attempt to determine the dates associated with the prophet Zoroaster's life. Priests had no Zoroastrian historical sources, and so turned to Babylonian archives famous in the ancient world. From these they learned that a great event in Persian history took place 228 years before the era of Alexander. In fact, this was the conquest of Babylon by Cyrus the Great in 539 BCE. But the priests misinterpreted this date to be the time the "true faith" was revealed to their prophet, and since Avestan literature indicates that revelation happened when Zoroaster was 30 years old, 568 BCE was taken as his year of birth. The date entered written records as the beginning of the era of Zoroaster, and indeed, the Persian Empire. This incorrect date is still mentioned in many current encyclopedias as Zoroaster’s birth date.
[edit]Modifications by Parthians, Ardashir I, Hormizd I, Yazdgerd III
The Parthians (Arsacid dynasty) adopted the same calendar system with minor modifications, and dated their era from 248 BCE, the date they succeeded the Seleucids. Their names for the months and days are Parthian equivalents of the Avestan ones used previously, differing slightly from the Middle Persian names used by the Sassanians. For example in Achaemenid times the modern Persian month ‘Day’ was called Dadvah (Creator), in Parthian it was Datush and the Sassanians named it Dadv/Dai (Dadar in Pahlavi).

In 224 CE, Ardashir I, founder of the Sassanid dynasty, added five days at the end of the year, and named them ‘Gatha’ or ‘Gah’ days after the ancient Zoroastrian hymns of the same name. This was a modification of the 365-day calendar adopted by Julius Caesar in 46 BCE, based on the Egyptian solar calendar. Iranians had known about the Egyptian system for centuries but never used it. The new system created confusion and met resistance. Many rites were practised over many days to make sure no holy days were missed. To this day many Zoroastrian feasts have two dates.
To simplify the situation, Ardeshir’s grandson, Hormizd I, linked the new and old holy days into continual six-day feasts. Nowruz was an exception, as the first and the sixth day of the month were celebrated separately, and the sixth became more significant as Zoroaster's birthday. But the reform did not solve all the problems, and Yazdgerd III, the last ruler, introduced the final changes. The year 632 was chosen as the beginning of a new era, and this last imperial Persian calendar is known as the Yazdgerdi calendar.