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How Did We Get Our Calendar?

Updated on September 28, 2010

The calendar is a manmade system of dividing and measuring time. It involves the fixing of some definite era or point of time as a basis for reckoning (e.g: the Birth of Christ), and then the division of time into convenient periods.

These periods have, from earliest times, been taken from astronomical observation. The most essential are the year, the month, and the day.

A year is the period of time taken by the earth to complete one circuit round the sun. A lunar month is the period taken by the moon to complete one circuit round the earth. A day is the period taken by the earth to complete one revolution upon its own axis. But none of these periods is capable of convenient measurement in integral figures.

A solar year consists of 365 days, 5 hrs., 48 min., 46 sec., a period inconvenient in itself, but doubly so if divided into months. A lunar month consists of 29.53058 days, and 12 of these give only just over 354 days- 11 days short of the solar year. Thus the year cannot be divided into an equal number of days or months without an increasing accumulation of error, and the history of the various calendars that have been constructed is largely that of different attempts to reconcile the discrepancy between the solar year and the lunar year of 12 lunar months.

The Roman Calendar

The year was originally divided into ten months starting from March and ending with December, and this left around 60 days unaccounted for. Very early in Roman history the months of January and February were added to the end of the year to keep the calendar in step with the solar year. These intercalations were in general determined arbitrarily by some official.

Under the Roman republic the year averaged 355 days. March, May, Quintilis (later called July), and October had 31 days. The other months had 29, except February, which had 28. A month was added when necessary, usually every other year or at the discretion of the pontifex maximus, who was in charge of the calendar. The Romans began their chronology with the year of the founding of Rome, which is traditionally set at 753 B.C. in terms of the Christian calendar. The initials "A.U.C.," an abbreviation of the Latin word meaning "in the year of the founding of the city," preceded the year number.

The priests in charge of the intercalations abused their authority, and tended to declare as 'full' years those in which their friends were in office. It was to cure this abuse that Julius Caesar decided to reform the calendar, which was then over two months out of step.

The Julian Calendar

Under the Roman Calendar the pontifices often adjusted the calendar to lengthen or shorten an official's term or to manipulate elections. By 46 B.C., when Julius Caesar became pontifex maximus, calendar dates were unrelated to the seasons. Caesar realized the need to end the abuses of the calendar and saw the great advantages of using a uniform and consistent calendar throughout the Roman Empire.

Advised by the Greek astronomer Sosigenes of Alexandria he adopted a solar year of 365 days as the basis for a new calendar which began on 1 January 45 BC. To bring the vernal equinox back to 25 March the year 46 BC, the 'year of confusion', was increased to 445 days.

Authorities disagree about the precise nature and extent of Julius Caesar's reforms. There is good reason to believe, however, that Caesar divided the year into 12 months, giving 31 days to January, Sextilis (later called August), and December and 30 days to April, June, September, and November. He left March, May, Quintilis (July), and October with the 31 days they already had and February with its 28 days. His arrangement of the number of days in each month and the order of the months still survives in present-day calendars.

In this new Julian calendar the year was normally to have 365 days, but 45 BC and every fourth year thereafter were to be 'leap' years having 366. There were to be 12 months beginning with January and having 31 and 30 days alternately, except February which in ordinary years was to have only 29.

After Caesar's death in 44 BC, the seventh month, Quintilis, in which his birthday fell, was renamed July in his honour. There was some confusion at first about the leap years but this was corrected in the time of the Emperor Augustus, after whom the eighth month, Sextilis, was renamed, the month being given an extra day to make it equal to July. This extra day was taken from February. To avoid having three 31-day months in a row, the order 31,30 was reversed for the months September to December.

From AD 8 the Julian calendar with every fourth year a leap year was used without alteration until 1582, by which time the cumulative difference between the calendar year of 365.25 days and the solar year of 365.2422 days had resulted in the vernal equinox being on 11 March, while Easter, which was intended to coincide with the Jewish Passover, but whose date was determined from tables drawn up in AD 325 by the Council of Nicaea, had moved forward towards the summer.

Pope Gregory XIII set out to rectify this situation.

The Gregorian Calendar

The Julian calendar's year was 11 minutes and 14 seconds longer than the actual solar year, so that by 1582 the calendar had accumulated an error of ten extra days. As a result, Christian holidays, such as Easter, were being moved out of their traditional seasons. In order to correct this displacement, Pope Gregory XIII decreed in 1582 that ten days be dropped from that year. To prevent the error from happening again, the Pope further prescribed that leap year be omitted every 100 years, except when the number of years was divisible by 400. Therefore, the year 1600 would be a. leap year, whereas 1700 would not.

The Gregorian calendar was immediately adopted in most Catholic countries, including Spain, Portugal, and parts of Italy. Protestant countries accepted it somewhat later, as, for example, Germany in 1694 and England in 1752.

Since it uses the birth of Jesus Christ as its starting date, the Gregorian calendar is generally considered the Christian calendar. Dates within the Christian period are often given with the initials A.D., standing for Anno Domini ("in the year of [our] Lord"), and earlier dates are usually followed by B.C., standing for Before Christ. The dating of the Christian era from the birth of Christ was first proposed by Dionysius Exiguus, a Christian abbot of the 6th century A.D. This suggestion was formally adopted by Charlemagne in 800 A.D. An interesting example of the controversies centered around the calendar concerns the date of Christ's birth. Originally it was set at Dec. 25, 1 B.C., but modern scholarship places it at Dec. 25, 4 B.C.

This calendar was at once adopted by Spain, Portugal, France, and parts of Italy. Protestant countries were slower to accept it; it was introduced into Scotland in 1600, into the greater part of Germany towards the end of the 17th Century. In Great Britain and the American Colonies it was not adopted till 1752 when 2 September was followed immediately by 14 September. In England the mob went about crying, "Give us back our 11 days!" believing their lives had been shortened by that period. Russia, and other countries of the Eastern Orthodox communion, did not accept the reform until after World War I.

Calendar Reform

Although the Gregorian calendar is, on the whole, satisfactory, it still has defects. It divides the year into unequal halves, quarters, and months, thereby creating problems for statisticians and accountants. Moreover, because of the extra day in what would otherwise be an even 52-week year, each date falls one day later than it did in the preceding year. As the days shift, the number of working days per month also changes, and businessmen have no precise way of comparing production from one year to the next. Businessmen and educators also waste much time on adjusting operations and schedules to the shifts of the calendar. In addition, holidays with fixed dates, such as Christmas on December 25, fall on a different day of the week each year. On the other hand; there are holidays, such as Thanksgiving Day and Labor Day, that fall on the same day but on a different date each year.

Various suggestions for rationalising the Gregorian year have been made. One scheme calls for 13 months of 28 days plus a New Year Day and, when required, a Leap Year Day as special holidays outside the normal sequence of seven-day weeks.

To overcome these defects, other calendars have been proposed. The International Fixed Calendar would divide the year into 13 months of 28 days each, with each month beginning on a Sunday. An extra day, called Year Day, would follow the end of the last month to effect a 365-day year. In leap years a Leap Day would be added following June 28. While this calendar is uniform, the main objection to its use is that it has an uneven number of months and does not divide the year into the even quarters and halves required in business and statistics.

A less radical alteration is advocated by the World Calendar Association of New York. Their calendar consists of four equal quarters each beginning on a Sunday with a month of 31 days and followed by two months of 30 days. Here again New Year's Day and Leap Year Day (between June and July) would not be included in the normal weekly sequence.

Holidays, birthdays, and anniversaries would always occur on the same day, making it easier for people to plan and schedule the use of time.

The World Calendar was brought before the United Nations in 1954. Its leading supporter was India, which wanted an orderly system to replace its 30 different calendars. Many countries, however, including the United States, disapproved of it because the World Day at the end of the year would interfere with the regular procession of Christian and Jewish Sabbaths, as well as with other religious observances. A similar system, the Perpetual Calendar, has also been proposed without success. Since the calendar is intricately involved in man's social, economic, and religious activities, people have generally resisted calendar changes.


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    • profile image


      7 years ago


    • munirahmadmughal profile image


      9 years ago from Lahore, Pakistan.

      "How we got our calander?"

      The hub is interesting and informative.

      Both Sun and Moon have their role in the matter of the time which is passing on. A year is of 12 months agreed upon by all, a weekof sevendays, a day and night of 24 hours, an hour of 60 minutes and a minute of sixty seconds. Thanksgiving is due on coming in and going out of the same breath. The favours of the Creator are open and hidden on the earth. Let us play our role in a manner that dignity of mankind prevails throughout. Time is immemmorial but its beginning for our purpose is from the moment the first man came on the earth and the last man will breath his last.Hence calender and calculation was there, other wise the many things could not be performed in time. Non preservation of that record is another thing. But historical researches and excavations are unearthing many a truth. Man can do anything according to his capacity. He is answerable according to his capcity. Addition of a single good act may be so useful that it may have its good effect for centuries. To remain after the truth is called research. Hence it is commendable. Research as been correct or erroneous is a separate issue and will be measured on the scale of good or bad intention. But the awareness and lack of awareness are certainly not equal. May God bless all.

    • darkside profile imageAUTHOR


      9 years ago from Australia

      LOL @ traderx's comment. :D

    • traderx profile image


      9 years ago from Las Vegas

      I thought the calendar was invented by Hallmark ...

    • Eileen Hughes profile image

      Eileen Hughes 

      9 years ago from Northam Western Australia

      That was in credible I have often wondered how they did it and believed it to have come from the romans. Now we all have learnt something, tar for that

    • profile image


      9 years ago

      fascinating. (said in Spock's voice)

    • prettydarkhorse profile image


      9 years ago from US

      very nice information, hey darkside I came by to greet you Happy holidays to you and yours, Maita

    • HubCrafter profile image


      9 years ago from Arizona

      I'm with Nick Author...(quote)

      ..."so the Mayans believe the world will end there anywhere I can go and get the full prediction?"

      But here's the version we have at MY house...

      My wife says, "There is absolutely NO chocolate left in this house...".

      So my wife acts like the world's gonna end..

      So, I gotta know..."Is there anywhere I can go and get the Full Monty of chocolate goods at 3 AM?"

      ...I'm tryin ta save the world here.

      Oh, yeah. Darkside. Nice Hub. You like covered the whole calendar thing in like...months. Seemed like months. Or monks. Whatever.

      LOL. My bad. Just havin fun witcha. Good job.


    • profile image

      Nick Author 

      9 years ago

      so the Mayans believe the world will end there anywhere I can go and get the full prediction?

    • profile image

      Nancy's Niche 

      9 years ago

      Great article and it would be interesting why the Mayan calendar was left out. Maybe you will write your next article on that particular mystery... ((:-o

    • Petra Vlah profile image

      Petra Vlah 

      9 years ago from Los Angeles

      Great and infrmative hub Darkside. Thank you

    • Petra Vlah profile image

      Petra Vlah 

      9 years ago from Los Angeles

      Great and informative hub; well reasurched.

      Strange that the Mayan calendar was not taking into account by the sources you used for reasearch; their knowledge of astronomy was impressive as were their engineering abilities (both based on mathematics)

    • darkside profile imageAUTHOR


      9 years ago from Australia

      Says, no idea. In researching this hub I looked at the calendars that influenced the one we use today, and the Mayan calendar, as far as I'm aware, wasn't taken into account at all.

    • dusanotes profile image


      9 years ago from Windermere, FL

      Thanks, darkside, for a great Hub. Thank good ness for Gregory 8th in eliminating those ten extra days. Otherwide, Christmas might end up in January...wouldn't that be a shame!

      I love Christmas right where it's at. I thought the part about politicians manipulating the calendar to get some more time on his "political clock" was interesting. To lengthen or shorten an official's term or to manipulate elections is something our president, Barak Obama, hasn't thought of - or has he? I think he's somewhat of a dictator already, so I wouldn't be surprised if he came up with a third term of office - all when we should be tightening up term limits here in the U.S. There's already too much spending corruption. Why extend the misery? Thanks for your very fine Hub. You need to check out my Hubs. My latest thing is a novel I'm publishing each Friday on Hub pages. Check it out. It's called Dragon Hunter. No, it's not sci-fi, but real current suspense stuff. Good work,

      Don White

    • profile image


      9 years ago

      Very interesting & informative! I'm wondering if you know anything about the line of thinking that predicts a global phenomenon to occur in December, 2012--the supposed end of the Mayan calender...

    • Dame Scribe profile image

      Dame Scribe 

      9 years ago from Canada

      Informative as usual, DS. Great information and somebody always wants credit to make changes, dont they? Excellent writing! :)

    • Raging Bull profile image

      Raging Bull 

      9 years ago from Melbourne, Australia

      Hi darkside, a very well written and informative hub. My daughter and I have always maintained that the way time is measured has been wrong and is out of line with the Universe. I'm personally more in tune with the Mayan calenders.

      Cheers Billie


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