The Calendar

The aim of the calendar is the past or future, to show how many days until a certain event occurs during harvest or a religious festival, or the time that something important has happened. The first calendar must have been strongly influenced by the geographical situation of the people who made them. In cold countries, the concept of the year was determined by the seasons, specifically in the late winter. But in hot countries, where the seasons are less marked, the Moon has become the basic unit to calculate the time of an old Jewish book says that "the moon was set for counting day."

Most of the oldest calendars were lunar calendars, based on the time interval from one new moon to another, called a lunation. But even in hot weather there are annual events that do not pay attention to the phases of the moon. In some areas, it was a rainy season in Egypt was the annual flooding of the Nile. The calendar had to account for these annual events as well.

History of the Egyptian calendar

Egyptian year coincided exactly under the sun only once in 1460 years

The ancient Egyptians used a calendar with 12 months of 30 days each, totaling 360 days a year. Around 4000 BC they added five extra days at the end of each year to make it more in line with the sun years.1 These five days became a festival because it was considered unlucky to work during this period.

The Egyptians had calculated that the solar year was actually closer to 3651 / 4 days, but instead of that day, a jump every four years because of the breaking day (as we do now), left fourth day accumulates. When in 1460 calendar year, or four periods of 365 years, 1461 years, Egypt had passed. This means that over the years, the Egyptian months fell to synchronize the seasons, so in the summer months at the end he fell in the winter. Only 1460 years after the calendar year at the same time, just the calendar year.

In addition to the calendar of civic activities, the Egyptians also had a religious calendar based on lunar cycles and 291/2-day was closely linked to agricultural cycles and movements of the stars.

History of the Roman (Julian) Calendar

The Romans were superstitious than even numbers were unlucky, so that their months were 29 or 31 long days

When Rome emerged as a world power, was the difficulty of making a calendar well known, but the Romans complicated their lives because of their superstition that even numbers were unlucky. Thus, their months were 29 or 31 long days, except February, which was 28 days. But four months of 31 days, seven months and 29 days a month of 28 days added to only 355 days. Therefore, the Romans invented an extra month called Mercedonius 22 or 23 days. It was added every two years.

Even with Mercedonius, the Roman calendar eventually became as Julius Caesar, advised by the astronomer Sosigenes, ordered a thorough reform. 46 BC was 445 days long by imperial decree, the calendar back in step with the seasons. Then, the solar year (with a value of 365 days and 6 hours) was the basis of the calendar. Months are 30 or 31 days long, and to care for six hours, every four years there was a year of 366 days. Moreover, Caesar decreed the year began with the first of January, not the vernal equinox in late March.

This calendar was the Julian calendar named after Julius Caesar, and continues to be used by Eastern Orthodox churches for holiday calculations to date. But despite the correction, the Julian calendar still 111 / 2 minutes longer than the actual solar year, and after several centuries, added another 111 / 2 minutes until.

The Gregorian Calendar

The Julian calendar is deleted

In the 15th century, the Julian calendar had moved behind the solar calendar for about a week, so that the spring equinox was falling around March 12 instead of around March 20. Pope Sixtus IV (who reigned from 1471 to 1484) decided that a further reform was necessary and called the German astronomer Regiomontanus to Rome for advice. Regiomontanus came in 1475, but unfortunately died soon after, and the Pope reform plans died with him.

Then in 1545, the Council of Trent authorized Pope Paul III to reform the calendar once again. Most of the mathematical and astronomical work was done by Father Christopher Clavius, SJ The immediate correction, advised by Father Clavius ​​and ordered by Pope Gregory XIII, was that Thursday, October 4, 1582, should be the last day the Julian calendar. The next day would be Friday, October 15. For accuracy at long range, a formula was proposed by the Vatican librarian Aloysius Giglio was adopted: every fourth year is a leap year unless it is a century, 1700 years or the 1800th year of the century can be leap years if divisible by 400 (eg 1600 and 2000). This rule eliminates three leap years in four centuries, making the calendar sufficiently precise.

Despite the revised rule for leap years is a calendar year average is still about 26 seconds longer than the orbital period of the Earth. But the difference is 3323 years to build up one day.

History of the lunar calendar

Lunar calendar is based on ancient Chinese, Babylonians, Greeks and Jews

During the ancient lunar calendar is better to estimate the solar calendar year based on 19 years, 7 of these 19 years to 13 months. Period included a total of 235 months. Still in use lunation value of 291 / 2 days, this made a total of 6.9321 / 2 days and 19 solar years added up to 6,939.7 days, the difference in just one week per period, and about five weeks per century.

Up to 19 years, needed adjustment, but became the basis of the calendar, the ancient Chinese, Babylonians, Greeks and Jews. The calendar itself was used by the Arabs, but Muhammad later forbade shifting from 12 months to 13 months, so that the Islamic calendar is a month now about 354 days. As a result, the month of Islamic calendar, as well as Muslim religious festival, wandering in all seasons of the year.