Shin Nomoto: The Islamic World and Various Calendars

2023/02/15

A traveler visiting an Islamic country is greeted by the call to prayer (Adhan) heard from the tower (minaret) of a nearby mosque. In particular, the profound impression of the dawn call ("Prayer is better than sleep, God is great...") has often been written about. Let us take a brief look at the calendars used in the Islamic world, starting from the day in terms of Islamic religious practice, and then in the order of week, month, and year. We will also look at the issue of calendars from the periphery, unrelated to religion.

Muslim prayer is performed five times a day—dawn, noon, afternoon, sunset, and night—but in the Middle East, there is a custom that a "day" begins at sunset and ends at sunset. In other words, "Friday" of a certain week begins at sunset on Thursday and ends at sunset the following Friday. Because the length of daylight changes every day, the times for prayer must be determined in detail daily. Before the modern era, major mosques in the region had timekeepers who determined prayer times by observing the movement of the sun. Furthermore, based on Babylonian and Egyptian traditions, the week consists of seven days, the same as in Judaism and Christianity. As the day of communal prayer, Friday was designated in Islam, in contrast to Saturday in Judaism and Sunday in Christianity, and many countries still officially observe it as the weekly day of rest.

Now, regarding the month and year, the Islamic religious calendar is a lunar calendar (approx. 354.37 days per year) based on the cycle of the moon's phases (approx. 29.53 days). It begins on the first day of the first month (Muharram) of the year (July 15, 622 AD) when the Prophet Muhammad (c. 570–632) performed the "Hijra" (migration) from his hometown of Mecca to the new land of Yathrib (later Medina [City of the Prophet]). This is known as the Hijri lunar calendar, where each month consists of 29 days for even months and 30 days for odd months, with one day added to the last month in 11 years out of every 30. Naturally, this calendar creates a discrepancy with the solar calendar (approx. 365.25 days per year) based on the Earth's orbital period around the sun. Therefore, during the famous month of Ramadan, the "month of fasting," people abstain from food and drink from dawn to sunset, but this may fall in winter when days are short, or in summer when days are long and the heat is taxing on the body. Incidentally, the beginning of a month is considered to be when the new crescent moon is confirmed by the naked eye in the evening sky after sunset, so the end and beginning of a month may differ by one day from the date determined by calculation. It is tough if Ramadan does not end and fasting continues for another day, but the sense of accomplishment upon completing it must be exceptional.

However, the lunar calendar is extremely difficult to use for agricultural activities and for collecting taxes based on those harvests. Therefore, in Japan and China, lunisolar calendars were used, incorporating devices such as inserting an intercalary month every two or three years so that the calendar and seasons would not drift significantly. In the Arabian Peninsula, there was also a lunisolar calendar with intercalary months before Islam, but it had already fallen into disuse by the time of the Prophet. There is a theory that attributes the cause of this to a revelation in the Quran, Chapter 9, Verses 36–37, which condemns the alteration of the twelve months ordained by God, but there are other theories and a definitive conclusion is hard to reach.

Eventually, the Hijri lunar calendar came to be used alongside solar calendars that were dominant in the regions conquered by Arab Muslims from the mid-7th century onwards. These included the Julian calendar of the former Roman Empire and the Iranian calendar centered on the vernal and autumnal equinoxes since the Sasanian Empire (224–651), used to coordinate agriculture and tax collection periods. The financial calendar of the Ottoman Empire was also based on the Julian calendar. In Egypt, there is an agricultural calendar called the Coptic calendar, which improved upon the ancient local calendar (consisting of 12 months of 30 days each for a 365-day year, with 5 days added at the end). It adds an extra day every four years, and the beginning of the year corresponds to August 29 of the Julian calendar to coincide with the flooding of the Nile.

The first day of the year in the Iranian calendar is called Nowruz ("New Day" in Persian) and is linked to the vernal equinox. However, according to common theory, the year was fixed at 365 days after the fall of the Sasanian Empire, and the date was inconsistent due to tax collection timing issues. It was the Jalali calendar, created during the reign of Malik-Shah I (r. 1072–92) of the Seljuk Empire, that fixed it to the vernal equinox. This calendar has 365 days in a year with a leap year every four or five years. In these Iranian calendars, beautiful names of angels unique to Iran or names of holy beings are used for the names of each month. Finally, the Solar Hijri calendar, one of the current official calendars of Iran, was established in 1925, and a similar Solar Hijri calendar is used in Afghanistan.

Another interesting aspect is the twelve zodiac signs (the Twelve Earthly Branches) adopted by Turkic and Mongol peoples from China. This was brought to Iran and its surroundings along with the great Mongol conquests of the 13th century. The twelve animals were adopted in the same order, and even today, descriptions of the year and fortune-telling are included in Iranian folk calendars.

Many calendars have been omitted here; the diversity of calendars in the Islamic world increases even further if those of the Indian subcontinent and Southeast Asia are included. Since the 19th century, the Gregorian calendar (the current Western calendar) has been added and is officially adopted in many countries. In this way, the Islamic world maintained a pure lunar calendar as its religious calendar, while on the other hand, many pre-Islamic calendars remained for agriculture and finance. These were further improved, and with the addition of calendars from foreign peoples, a wide variety of calendars have been used. This fact speaks to the cultural diversity of the Islamic world and the flexibility of people's thinking.