The Calendar
For a long time, people were able to measure the passage of time by keeping track of the changing phases of the moon. Eventually many societies developed systems of measuring the passage of time called Calendars. The three basic units of most Calendars-day, month, and year- are determined by the movements of the earth and the moon. A Day is the time required for the earth to make one rotation on its axis, about 24 hours. A Month is the time required for the moon to go through one cycle of phases as it orbits the earth, or 29.5 days. A solar year is the time required for the earth to make one orbit around the sun, about 365.24 days.
The different lengths of time that are needed for the movements of the earth and the moon cause problems in creating any calendar. First, the earth does not make a whole number of rotations on its axis in the time that it makes one orbit around the sun. A calendar year of 365 days is too short, while a calendar year of 366 days is too long. Therefore the number of days in a calendar year must vary. The variation is to compensate for the extra one-quarter day required for the earth to orbit the sun.
The second problem is that the earth does not make a whole number of rotations on its axis in the time the moon orbits the earth. A month of 29 days is too short, but a month of 30 days is too long. Thus the number of days in a month must vary in order to account for the extra one-half day in a cycle of the phases of the moon.
Third, the moon makes between 12 and 13 orbits around the earth in the time that the earth orbits the sun. Therefore the number of months in every year cannot exactly correspond to actual movements of the earth and its moon.
The different lengths of time that are needed for the movements of the earth and the moon cause problems in creating any calendar. First, the earth does not make a whole number of rotations on its axis in the time that it makes one orbit around the sun. A calendar year of 365 days is too short, while a calendar year of 366 days is too long. Therefore the number of days in a calendar year must vary. The variation is to compensate for the extra one-quarter day required for the earth to orbit the sun.
The second problem is that the earth does not make a whole number of rotations on its axis in the time the moon orbits the earth. A month of 29 days is too short, but a month of 30 days is too long. Thus the number of days in a month must vary in order to account for the extra one-half day in a cycle of the phases of the moon.
Third, the moon makes between 12 and 13 orbits around the earth in the time that the earth orbits the sun. Therefore the number of months in every year cannot exactly correspond to actual movements of the earth and its moon.
The Julian Calendar
In 738 B.C. the leader Romulus supposedly introduced the first calendar used in Rome. This Calendar was a 304 days divided into 10 months. Later rulers made various modifications in the calendar, it was about 3 months behind the seasons at the time of the Julius Caesar's reign. They divided the year into 12 months. 11 of those months had 30 or 31 days. Febuary had 29 days, but later one day was moved from febuary to August leaving only 28 days. Every fourth year was a leap-year, a year with an extra day in it. According to the Julian Calendar, which was used for over 1,500 years, the year was 365.25 days long. This however, was about 11 minutes longer than the actual solar year. Each year the difference between the calendar and the solar year increased.
The Gregorian Calendar
By 1580, the calendar was about ten days ahead of the seasons. to correct this discrepancy, Pope Gregory the eighth ordered that ten days be dropped from the month of October in 1582. This made up for the error that had built up over previous centuries. This Calendar is the revised version of The Julian Calendar, and is the Calendar currently used in most of the world. Compared with previous calendars, the gregorian calendar is so accurate that the calendar year is only 26 seconds longer than the solar year. As a result, the current Gregorian calendar accumlates an error of less than one day over a period of 3,000 years.
Current Calendar Reform
Many reformers have proposed to simplify the current calendar. Some of these recommended that all months and years begin on the same day of the week. They also try to give all months nearly the same number of days.
One proposed Calendar is called the Thirteen-Month Calendar. This Calender would consist of...
- four weeks per month
- a new month called Sol (would come between June and July)
- a year day, belonging to no day or Month, it would fall at the end of each year.
- a leap- year at the end of Sol, every 4 years
One other proposal is the world calendar. It would have...
- 12 months of either 30 or 31 days
- world day would be placed at the end of each year
- leap-year day would be added at the end of June, every 4 years
One proposed Calendar is called the Thirteen-Month Calendar. This Calender would consist of...
- four weeks per month
- a new month called Sol (would come between June and July)
- a year day, belonging to no day or Month, it would fall at the end of each year.
- a leap- year at the end of Sol, every 4 years
One other proposal is the world calendar. It would have...
- 12 months of either 30 or 31 days
- world day would be placed at the end of each year
- leap-year day would be added at the end of June, every 4 years