Thousands of years ago, people depended on natural events to keep track of time such as the rising of the sun, the length of shadows, the phase of the moon or the position of certain stars in the skies. As civilization became more complicated, better ways of measuring time were needed, hence, the creation of the calendar system. Today, calendars can be readily used to track time and mark important events.
The international calendar that is used today evolved from ancient calendar systems which were implemented hundreds of years ago. These are a few of the historical and influential calendar systems.
The Sumerian Calendar - 6th century B.C
The Sumerian calendar had 12 lunar months where each month had 29 or 30 days. The sighting of the new moon marked the beginning of each month. The months had no uniform name because of the diversity of religions in Sumeria.
The scribes and scholars then referred to the months as "the first month", "the third month" and so on. An extra month was interpolated every three years to keep the lunar year of 354 days with the 365.25 days of solar year. The Sumerian calendar did not divide the months into weeks.
The Mayan Calendar
This ancient calendar system from the Maya civilization was one of the most complex calendars along with the other Mesoamerican calendar systems. The Mayan calendar had two years: the Sacred Round which was used for religious purposes and the Vague Year which was when they did the day-to-day things such as planting crops.
The Sacred Round consisted of 2 cycles :
1 cycle was composed of 20 named days
1 cycle was composed of 13 numbered days
Each of these cycles continuously repeated to make up 260 days.
The Vague Year consisted of 18 months, each month having 20 days and an intercalary month which consisted of 5 days. The intercalary month was included to keep the calendar consistent with the solar year. This calendar is closer to the modern calendar as it followed the solar cycle lasting 365 days.
The Athenian Calendar
The Athenian calendar was a luni-solar calendar made up of 12 months with 354 days. Each month alternated between 29 or 30 days long. An extra month was added every other year to keep the calendar in line with the 365.25-day solar year.
The months of the Athenian calendar began with Hekatombion and ended with Skirophorion. The intercalary month usually came after the month of Poseidon and was called the second Poseidon.
The Roman or Julian Calendar
The Romans adopted the 304-day calendar which was divided into 10 months that began with the month of XI Kal. Januarius and Februarius were added as intercalary months to fill the gaps. The Romans believed that the even numbers were unlucky and with this superstition in mind, the calendar months they created were 29 or 31 days in length but the month of Februarius was an exception as it only had 28 days. And because the total number of days when added was only 355 days, they created the Mercedonius as an extra month which had 22 or 23 days and was added every two years.
Later, Julius Caesar found the calendar system to be inaccurate and so he made some drastic changes. The new calendar was to begin on January 1 and it ran over 365 days with December 31 as the end of the year. Augustus then made further adjustments to this system and introduced the concept of a "leap year" in AD 4. The result is the invention of the Julian calendar. This calendar system was widespread and used in Europe until the year 1582. The calendar we use today was fashioned after the Julian calendar system.
The Julian calendar had months with fixed lengths, and every four years, a day was interpolated to keep in synchrony with the calendar year. The Julian calendar's principles are still utilized by the chronologists today. However, tracing its history, the year -45 had been confusing when Julius Caesar interpolated 90 days so that the months in the Roman calendar would be synchronized with the respective seasons. When Sosigenes, an astronomer from Alexandria offered to resolve this matter, Julius Caesar designed a solar calendar with fixed-lengths of twelve months and an intercalary day which was inserted every four years. This resulted to the average length of the Julian calendar year of 365.25 days and was consistent with the tropical year.
However, after the death of Julius Caesar the Romans who were authorized to revise the calendar misused the leap-year rule. The intercalary day was added every third year instead of the four-year rule. And it was Emperor Augustus who corrected this situation and made the Julian calendar usable again. The Julian calendar was utilized through the Middle Ages. Up to this day, the Eastern Orthodox churches used the Julian calendar for holiday calculations.
The Gregorian Calendar
Pope Gregory XIII (1502 – 1585) was the one to alter the Julian calendar and transformed it to "Gregorian". Reforming the method of calculating when Easter would be resulted in a need to reform the old calendar. This was the birth of the Gregorian calendar. By changing the calendar Gregory was declared the "Roman Antichrist" by the Protestant tract writers because they thought that Gregory intended for true Christians to deviate their worship from the correct days to incorrect days.
The 7-day week was adopted from the Hebrew calendar. The notion of 7-day weeks originated from the ancient Babylonian calendar. It is believed that the Babylonians chose this division of 7 days to represent the seven heavenly bodies that they worshiped as gods. These gods include: the sun, the moon, and five planets which are visible to the naked eye.
The modern calendar that we use today is the Gregorian calendar. ALthough many cultures continue to follow their own calendar systems often for religious purposes, the Gregorian calendar remains international.
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