The following is where I left off yesterday finishing with the Julian Calendar to other calendars:

"The Naming of the Months on your Calendar

The new calendar spread across the empire and also into neighboring states and client kingdoms, where calendars became 365 days with one leap day, initially every three years but eventually every four years.

The names of the previous months remained mostly unchanged. January honored the god, Janus who symbolizes “new beginnings.” These gods are interesting to study for many reasons, but the god Janus had one head, but two faces. In honor of this god, one face could look forward to the future, and one face looked back to the previous year. Every month had deep reflections, thoughts, concerns, and deliberations to come to a consensus of opinions. The calendar was vastly serious to these people.

February is likely to derive from the Februa festival. March was for the god Mars. The origins of April, May, and June are unclear; but may have been derived from the Etruscan god Apru, and the gods Maia and Juno respectively. An alternative theory is that April comes from the Latin word “aperire,” to open, while May and June are old terms for “senior” and “junior.”

The remaining months were named after their order in the calendar. Quintilis was the fifth month; Sextilis, the sixth; September, the seventh; October, the eighth; November, the ninth; and December, the tenth. The Julian reform pushed the months down the calendar so that December became the twelfth month without changing its name. Quintilis, however, the birth month of Julius Caesar, became Iulius (“July” in English), and Sextilis became Augustus or August.

Other emperors tried to rename months too. Caligula tried to call September “Germanicus” to honor his father. Nero wanted to April to be called “Neroneus.” Domitian wanted October to become “Domitianus.” These names didn’t stick.

The History of the Gregorian Calendar

The Julian Calendar worked pretty well, but it wasn’t wholly accurate. The calendar assumed that a year had precisely 365.25 days in a year. The Earth takes 365.2422 days to revolve around the sun and that difference of eleven minutes every year was enough to push the calendar out of alignment with the equinoxes by about three days every 400 years.

By the eighth century, Saint Bede, an English Benedictine monk, had already noticed that the calendar had drifted by three days. Five hundred years later, Roger Bacon figured that it was a good week or so out of alignment; and by 1300, Dante talked of the need for complete calendar reform.

The drift of the calendar proved a problem for the church. The celebration of Easter was determined by the date of the spring equinox which the church had established fell on March 21. By the sixteenth century, the equinox fell about ten days earlier.

In 1545, work on changing the calendar got underway. The Council of Trent authorized Pope Paul III to adjust the dates so that the spring equinox matched once again the equinox at the time of the First Council of Nicaea in 325. The Nicaean Council also asked for a new way of keeping time to prevent Easter from drifting through the calendar again.

Aloysius Lilius Fixes the Calendar
Whatever the faults of the calendar, work in the sixteenth century took an incredible amount of time. It wasn’t until 1577 that the reform commission asked mathematicians for their contributions. The winning proposal came from Aloysius Lilius, an Italian doctor and astronomer. He suggested the leap year should first be canceled for the next forty years, allowing the equinox to catch back up with the calendar. He then suggested a new formula to stabilize the calendar.

Instead of adding a day every four years, if a leap year fell on a year divisible by 100, a day would only be added if that year were also divisible by 400. In the year, 1600, one day would be added and would become a leap year, but not in 1700, 1800 or 1900. 2000 was a leap year, but 2100 will not be a leap year. The result would be the addition of a leap day on only 97 days out of every 400, instead of a leap day added every 100 days. These additions and subtractions ensured that the calendar was regularly brought back into alignment.

The new calendar was adopted on Friday, October 15, 1582, during the papacy of Gregory XIII. The previous day, according to the Julian calendar, was Thursday, October fourth. Spain accepted the new calendar immediately, followed by Spain, Portugal, France, Poland, Italy, the Catholic Low Countries, and Luxembourg. The Kingdom of Bohemia adopted the calendar two years later. Prussia accepted the calendar in 1610. Protestant countries were slower to adopt the calendar, concerned that it would bring their countries closer to Rome. Britain didn’t choose the Gregorian calendar until as late as 1752. Greece waited until 1923 to adopt the calendar, and Turkey until 1926.

The Gregorian calendar repaired the Julian calendar’s error of one day every 128 years, replacing it with an error of one day every 3,030 years. Sir John Herschel, a nineteenth-century English mathematician, suggested increasing the calendar’s accuracy by not making the year 4000, and its multiples, a leap year. He was ignored.

Local Calendars Still in Use
We’ve moved through several thousand years of history. We’ve seen calendars change from stone arrangements used to mark the solstice and predict the return of migrating animals; through the tracking of the stars and the counting of months. Mostly what we’ve seen through the metamorphous of the calendar, is various cultures and empires struggling to produce a way of counting days and months in a year. Their difficulty was taking into account the extra quarter-day that the Earth uses to get back to its starting point. Without taking that time into account, they’d see the calendar slip through the year. We’ve also seen some creative names for the months those calendars have come up with.

The introduction of the Gregorian calendar set the seal on the calendar’s development. Lilius’s correction, introduced during the papacy of Gregory XIII, meant at last that the year was always accurate and never needed correcting—or at the very least, only occasionally. The calendar’s spread across Christendom, and from there around the world, means that the globe now shares a single way of marking time.

The Continued Use of the Julian Calendar
The calendar is not the only way to mark time. The Gregorian calendar isn’t the single calendar still in use. While everyone might be able to find the same date on the same calendar, around the world, people still use other calendars. Even in Europe, the Gregorian calendar didn’t reach everywhere. On the autonomous province of Mount Athos in Greece, the Julian calendar still reigns supreme. The province is made up of twenty Orthodox monasteries, and entry is forbidden on the island to women.

Orthodox churches, if not Orthodox countries, remained with the Julian calendar. These countries even rejected a lunar calendar that would match the Gregorian calendar until the year 2800. The calendar was suggested at a synod (congress, committee), in Constantinople in 1923. Apart from the Estonian and Finnish Orthodox Churches, Orthodox churches continue to celebrate their Christian festivals according to the Julian calendar, and not the Gregorian calendar. Other areas and religions have also stuck with their traditional calendars.

The Hebrew Calendar
Israel uses two calendars: the Gregorian calendar; and the Hebrew calendar. The Gregorian calendar will be used for all secular activities, for fixing the time of the school breaks, for arranging business meetings, and for celebrating birthdays. But the dates of religious festivals — and there’s a Jewish holiday almost every month — are determined by the Hebrew calendar. Similarly, the Jewish calendar is used to determine the portion of the Torah to be read each Shabbat. It’s also used to fix the dates of memorials to commemorate the death of a relative.

The Hebrew calendar is strongly influenced by the Babylonian calendar, a result of the Jewish exile in Babylon which ended in the sixth century BCE. The Bible suggests that before the exile, the Hebrew calendar consisted of ten months of thirty days each. The Bible only names four months: Aviv (which means “spring”); Ziv, Ethanim, and Bul. These names are believed to be Canaanite. After the Babylonian exile, the names of the months more closely matched the names of the months of the Babylonian calendar.

One notable difference between the Gregorian calendar and the Hebrew calendar is how the days are measured. The Hebrew calendar regards a day as beginning at sunset. Shabbat starts when the sun sets on Friday evening. The Shabbat day ends when the sun sets the following day.

No less important though is how the months are measured. The Gregorian calendar is solar. It’s based entirely on the relative position of the sun to the stars. The Hebrew calendar is a lunisolar calendar, meaning that the months are based on lunar months (taking into consideration the phases of the moon) — and the years are based on solar years. This calendar has twelve lunar months that last either 29 or 30 days.

The Buddhist Calendar

Also adhering to the lunisolar calendar is the Buddhist calendar, primarily used in mainland Southeast Asian countries of Cambodia, Laos, Myanmar, and Thailand — with many many variations and versions in countries around the world. The traditional Buddhist calendar is mainly used for Theravada Buddhist festivals, and there is no longer an official Buddhist calendar status anywhere.

The Buddist calendar keeps track of the movements of both the Moon and the Sun, and mostly follows the Hindu calendar. This calendar is somewhat inaccurate when reflecting the length of a solar year and the onset of the seasons because of the “sidereal year,” and the 19-year cycle use to determine the distribution of leap years based on the length of a tropical year.

The Metonic Cycle

A solar year is eleven days longer than the twelve lunar months. These eleven days put the Hebrew calendar out of sync with the solar calendar. Without correction, the holidays would drift out of alignment with the seasons. The solution came with the addition of leap months. The Hebrew calendar doesn’t add leap months every four years, like the Gregorian calendar, but seven times every nineteen months.

The Metonic cycle is the work of Meton of Athens in the fifth century BC. Following the Babylonians, Meton noticed that nineteen years is almost exactly equal to 6,940 days. Adding the seven additional months, over nineteen years would be enough to correct the calendar.

Using the Metonic cycle isn’t the only complication. The calendar can also change to make sure that Yom Kippur, the Day of Atonement, does not fall immediately before or after Shabbat. The month of Kislev can lose a day, and the month of Cheshvan can add a day. The result is a reasonably complex calendar that many people generally ignore. The Hebrew dates will appear at the top of newspapers, but otherwise, people basically use these calendars to mark Jewish holidays.

The Islamic Calendar

The Jewish Calendar goes out of its way to remain in alignment with the solar calendar. The calendar also adjusts the lengths of the months. A holiday fixed by month shouldn’t clash with a holiday fixed by week. The Islamic calendar takes a much easier route. It doesn’t correct at all. It consists of twelve lunar months, which together number 354 or 355 days. That will consider the difference to the 365.25 days of the solar year. This calculation means that the Islamic calendar drifts by about ten days every year. The cycle only repeats every 33 lunar years.

The result is that Ramadan, the month of fasting, can take place in the summer or winter, depending on the position of the calendar. That may be why most Islamic countries only use the Islamic calendar for religious holidays and not for civil events. These public events are marked using the Gregorian calendar. The exceptions to the “civil event rule,” are the countries of Iran and Afghanistan, which use the solar Hijri calendar.

The Hijri Year

The Hijri year is also the foundation of the Islamic calendar. This calendar came about in the era in which Muhammad and his followers traveled from Mecca to Medina to form the first Muslim community. That event took place in 622 AD and marks the start of the annual count. According to the Islamic calendar, 2019 in the Gregorian calendar is the year 1440. (The Hebrew calendar makes the year 5779.)

The Islamic calendar contains twelve months, each of which begins with the start of the new lunar cycle. Each of the months also has its own significance. The months of Rajab, Dhu al-Qa’dah, Dhu al-Hijjah, and Muharram are considered sacred. Ramadan is a month of fasting. Shawwal means “raised” and is said to be when camels would be in calf; (with calf), meaning they are pregnant. Sha’ban means “scattered” and marks the time when Arab tribes scatter to find water. Dhu al-Hijjah is when the hajj, the pilgrimage to Mecca, is performed.

Two Countries, Two Months

Another challenge the calendar faces and creates is that most Muslim countries declare the start of a new month by observing the rise of the new moon. Each country will make its own observation. But the sun sets later as you head west, and the conditions may make the moon easier or harder to see in one particular place than another. The result is that two Muslim countries may be in different months at the same time.

There have been plans to try to get around the problem. Malaysia, for example, is one of several countries that start the month not when they see the new moon but at sunset on the first day that has moonset after the sunset. Some representative bodies have declared an intention to use calculations instead of observations to determine the months, but not all associations have agreed, and not all those that have declared an intention have carried the purpose out.

It’s a complicated business, and that means that not only is the Islamic calendar out of alignment with the solar year and the Gregorian calendar. The Islamic calendar is also sometimes out of alignment with other users of the Islamic calendar."

Well tomorrow we will continue to look at other calendars starting with the Chinese Calendar.

Reference: https://www.calendar.com/history-of-the-calendar/