Week and weekdays have important application in calendar systems both solar and lunar. Even though world’s different calendars vary in many calculation details and other features, the method of reckoning based on seven-day week is the same in all of them.

We know that number of days in a month or in a year is different in each calendar, even in the same calendar months different number of days (some months have 30 days some 31), and we also know that during the history there have been reforms to change this.

Number of days that are added in a leap year might also vary (1 day, 1 month, etc. ). However, the importance of week-based reckoning is that the number and sequence of days in a week will never change for any reason. The continuation of days does not follow any special system. In other words, “week-counting” in itself and without the need to any other system is considered a simple, accurate, and prevalent method in calendar calculation all over the world. This special feature has an important role in matching historical occasions and understanding how accurate some historical data are. The only different thing in week-based systems is the conventional holiday which varies from Friday to Monday in various religions and cultures.

Today, many assume that in Ancient Persia and in pre-Islamic Iranian calendar systems week was not used and as a result there was no name for week days. This assumption is very common and widely-held. Of course, it has its own reason as in none of the known ancient Iranian document from those periods we see any mention of week and weekday names. We also know that Sassanian calendar did not use week, and days of each month were simply known by their names. So far, we can assume that the official and state calendar of Sassanids did not take advantage of week concept; however, we cannot generalize this assumption to all periods, all calendars, all ethnicities, and all religions of Ancient Persia.

On the other hand, we are aware of the numerous distortions of Iran’s history and culture by Sassanids and especially by their mobads (Zoroastrian clerics). So we can safely assume that abandoning weekdays from calendar is a similar distortion. There is not enough evidence and document to prove this speculation; especially that Pahlavi texts and history books and chronicles of the ensuing periods are silent about this. Because the Pahlavi texts are usually the official opinions of the Sassanian state and its religious body and thus they had great influence on the history books of the later periods.

The author believes that week-based reckoning and weekday names existed in the Ancient Persia and it’s only the official Zoroastrian Sassanian calendar where it was absent. Five groups of evidence for this claim could be presented:

First, the seven days of the week are from the time immemorial based on the seven day crescents of the Moon and since the lunar calendar is the simplest and the earliest form of reckoning, and recognizing different crescents are the easiest and fastest ways of keeping track of time, no doubt the human societies from the oldest period had discovered this and taken advantage of it without any special training.

Second, Shahnameh by Ferdowsi mentions hafte (week in Persian) more than 120 times and charshanbe (Wednesday in Persian) twice:

The astronomer recommended King Bahram
Do not forget revelling on Wednesdays

Since Shahnameh is considered a faithful translation and transfer of stories and narrations of the Ancient Persia, it would be strange if Ferdowsi had used this concept without any support from the original documents and texts.
Third, the author in examining the solar calendar structure (commonly known as Zoroaster’s Kabaa or Cube of Zoroaster) in Nqash-e-Rustam has discovered mechanisms that were embedded therein to detect the last four weeks of the month of Shahrivar (the last month in Achaemenid calendar) and detail of this discovery is published in my book Astronomical and Calendar Structures of Iran (in Persian).

Fourth, Manichean texts prove the prevalent and widespread use of week days. In Manichean writings, found in Turfan and Mug Tag, Sunday and Monday are mentioned as “Mehr Ruz / Khwar Ruz” (day of Sun) and “Mah Ruz” (day of Moon) and are considered days of fasting in Manichaeism. Of course, in Manichean texts the thirty names of month days are also used along with names for week days. We also know that Monday was the sacred day and holiday in Manichaeism. (See A. Freeman, Researches in Mug Tag Texts, Moscow, 1962, in Russian).

Fifth, ancient Chinese texts and sources have reported the use of week in Ancient Persia and they even give the list of weekday names. An ancient Buddhist astronomical text, which was translated from Sanskrit into Chinese in 759 AD and Yang Ching Feng annotated it in 764 AD, mentions the name of weekdays in Chinese and provides their equivalent in Middle Persian (Pahlavi) and Soghdian languages. In this text, Iranian names for the weekdays, which started from Sunday, are given as follows: Yo-Shambat (the holiday), Do-Shambat, Seh-Shambat, Char-Shambat, Panj-Shambat, Shesh-Shambat, and Shambat. In the same text, the Soghdian equivalents of these names appear, again week starts with Sunday: Mehr Ruz (day of Sun), Mah Ruz (day of Moon), Bahram Ruz (day of Mars), Tir Ruz (day of Mercury), Ormazd Ruz (day of Jupiter), Nahid Ruz (day of Venus), and Jian Ruz (or Keyvan Ruz meaning day of Saturn). As it could be seen, these names are based on the seven heavenly bodies, i.e., the Sun, the Moon, and the five planets known in the ancient world. (For more detail, see Kung Fang Zhen, Terms from Iranian Calendar in Ancient China, translated into Persian by Prof. Mohammad Bagheri, published in the special issue of History of Science, Tehran, 1372 AH / 1993 AD).

Based on the evidences presented above in summary, it seems that weekdays, along with specific names, were used in calendars of Ancient Persia and even Sunday as the holiday in Christian calendar was adopted from Iranian calendar. We know that Sunday in both calendar means “day of Sun” (in middle Persian: Mehr Ruz, see above). However, under Sassanids and along with other numerous distortions that were made to the customs and culture of Ancient Persia, they dropped weekdays from their calendar and used only names for month days. They probably used the three di-designated days (di be Azar, di be Mehr, di be Din, i.e., days number eight, fifteen, and twenty-three) along with Ormazd (the first day of each month) as holidays in each month. We also need to mention that the names for thirty days of month is used in all Iranian calendars and this is not limited to Sassanian calendar only.
Reza Moradi Ghiasabadi
Translator: Yusef Amiri

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Weekdays at ancient Persia (Iran)
Reza Moradi Ghiasabadi
Translator: Saam Sheykh-ol Eslami

Week and seven weekdays has a lot of usage at solar calendars although different calendars have different details but in all of them week with seven days are the same we know days of month and year differs at different calendars and during history they had changed and also Leap years have more days.

Another important thing about week is that they never change at any calendar in other words weekly counting is the most accurate counting system this special characteristic has very important role on synchronizing different calendars. The only difference that they have is holiday (Friday to Monday) at different religions.

Nowadays a lot of people think that at Persian (Iranian) ancient calendars were no week so there weren`t any name for weekly days. This is a pervasive idea but this idea has its own reasons and that is at famous Persian ancient writings. There is nothing about names of weekly days and we know that Sassanid calendar had no weeks so days of month had names which people used them we know that at Sassanid official calendars there were no use of weeks but we cannot popularize it to all periods and all calendars.

At the other hand we know about Sassanid and Zoroastrian clergymen`s distort ants. So may be eliminating week from calendar was their affection to calendar. But for proving this idea we don`t have enough evidence. Specially because Pahlavi history and middle age writings say nothing about it, because Pahlavi writings were mostly viewpoint of Sassanid policy and religious policy had effect on writings after them. Writer thinks Persian ancient calendars had weekly counting but Sassanid official calendar didn’t have it here are four theories that proves it:

1- Weekly counting is an old counting system that has been used at lunar calendars. It is fastest and easiest way of counting dates and undoubtedly ancient nations have used them.

2- This item is Shahnameh Ferdowsi has used word week about 120 times and also 2 times Wednesday has been used as Shahname is reporting old Persian (Iranian) time and has translations of history writings is unlikely that without any concept of week these words has used.

3- Third one is writing the Manicheanists that has used week a lot “Tourfan”, “Mug- Tag”, Sunday and Monday are Mehr- rouz and Khowr- rouz and these two days used for getting fasten at writing the Manicheanists names of days at month has been used also and Monday was holiday.

4- Ancient Chinese writings reported Persian weekdays an old ancient Buddhist writing which (759 AC) has been translated from Sanskrit to Chinese “Gang Ching Fang” had written a purl about it (n 764 AC) he had written Chinese name of days and their equal middle Persian and Sogdian language at this writing we see names of Persian weekdays which start from Sunday: Yu- Shambat (holiday), Do- Shambat, Se- Shambat, Char- Shambat, Panj- Sambat, Shambat. At same writing their Sogdian equal are Mehr- Rouz, Khowrshid- Rouz, Mah- Rouz, Bahman- Rouz, Tir- Rouz, Ourmazd- Rouz, Nahid- rouz, Jian- Rouz (Keyvan- Rouz).

As we see these seven names came from seven stars: Sun, Moon and other know planets (at that time).

With this brief description about  the evidences  which came above it seems Persian (Iranian) ancient calendars used weekly days and Sunday as holiday. Sunday at Christian calendar came from Persain calendar at both calendars have the same meaning (Sunday= Khowrshid- Rouz). But during Sassanid a lot of things were sophisticated which weekdays are among them they used names of days at month their system had shortage for solving this problem they used “Dey” for eighth, fifteenth and twenty- third of each month. With Ourmazd (first day of each month ) these days were holidays. We should consider that these names had been used at all Persian calendars they weren`t just for Sassanid.

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