How and When Our Calendar Was Adopted

With a New Year on the horizon, here's how our current calendar was ordered into existence by Pope Gregory XIII, who followed the work of Roman emperor Julius Caesar


Our current calendar is named after a pope, but it all began with the most famous leader of the Roman empire.

Julius Caesar instituted the model for what our calendar is based on in 45 B.C. when he approved what was called the Julian calendar.

According to infoplease.com, that calendar consisted of 11 months of 30 or 31 days each with 28 days in February. Quite accurate for its time, but with a major flaw.

The calendar was off from the real solar year (the time it takes the Earth to circle the sun) by 11 minutes. Over the centuries, that added up.

By the late 1500s, the Julian calendar was off by 10 days from the solar year.

So, in 1582, Pope Gregory XIII approved a new calendar that include 365 days and a leap year every four years.

To catch up with the sun, the pope ordered the calendar to advance by 10 days. That officially happened on Oct. 15, 1582.

Not So Fast

Not every country immediately accepted the pope's decree and adopted the Gregorian calendar.

It took the British Calendar Act of 1751 to bring England and the American colonies into the fold. By then, the calendar was off by 12 days.

That adjustment was made the following year. In Britian and the colonies, citizens went to sleep on Sept. 2, 1752 and woke up to Sept. 14, 1752.

Other countries were even later. The Netherlands adopted the Gregorian calendar in 1698. Russia accepted it after the 1918 revolution. Greece came on board in 1923.

The Gregorian calendar is only 26 seconds different from a true solar year. That adds up to only one day every 3,323 years.

Old Calendars Die Hard

Many Orthodox churches still use the Julian calendar and they are now 13 days behind the Gregorian calendar.

Many Muslim cultures still use a lunar calendar based on the phases of the moon.

According to infoplease.com, ancient people drew up calendars to coincide with natural phenomena they observed such as phases of the moon and changes in the weather.

Some of our modern time categories are natural. A year is based on the Earth's revolution around the sun. A day records one rotation of our planet.

However, sequences such as months, weeks, hours, minutes and seconds are time divisions chosen by humans.

According to historyworld.net, the numbers we use today were chosen for their divisibility. For a day, 24 hours was chosen because 24 is divisible by a lot of other numbers. In addition, 12 hours was a convenient way to keep of track from dawn to dusk. Noon was the midpoint, or six hours on either side.

For an hour, 60 minutes was chosen, along with 60 seconds, because it too has a lot of factors.

Clocks that recorded minutes were first produced in the 14th century. Clocks that recorded seconds came 200 years later.

The origin of the seven-day week is less certain. According to webexhibits.org, some scholars believe it's based on the creation of the Earth in the Bible where it says God worked for six days and rested on the seventh.

Others, however, say the seven-day week predates the Bible. Theories include ancient people basing the week on the seven known celestial bodies in ancient times or that seven days is close to one moon phase.

Do you prefer to use a modern electronic or online calendar, or an old-fashioned paper one? Share your thoughts in the comments area below.

Steve Wozniak January 02, 2013 at 01:35 AM
In my opinion, months were a dumb idea. The year was neatly separated just by day numbers. You'd get just as much in your mind by hearing a day number than a month and day. Weeks would be 10 days long. The first digit would give you an instant idea of the season and the second digit is how many tenths into that season. It would have worked very well. But think back. Roman numerals were not the same as our digits today. Day numbers would not have worked well with Roman Numerals. Vanity was surely a part of this month idea too. My opinion is that logic should rule. Don't assume that because we do something a certain way it's the best way.
Gary Hinze January 02, 2013 at 04:08 AM
Logic won't work here. The year is based on how long it takes the earth to go once around the sun by reference to the background stars. The month is based on the phases of the moon, which are determined by the time it takes the moon to orbit the earth, the time it takes the earth to orbit the sun and their orientation to the sun. The months are also related to the constellations seen at night. The day is based on the time it takes the earth to make one revolution relative to the sun, which is not the same as relative to the background stars. The days of the week are named for the observed planets, using the names of the associated gods. The twenty three degree tilt of the earth's axis produces the seasons, which correspond to the months. None of these numbers is rationally related to the others. They do not have a common start time. Not only that, but they vary. Things do not ever get back to exactly where they were, all at the same time. The earth's orbit is not perfect, it is affected by the other planets and wobbles. The earth's axis also wobbles. There is no "harmony of the spheres". We live in a irrational world. The best we can do is an approximation, with an occasional adjustment. CalTrans uses a calendar with days numbered consecutively. Other agencies also use this calendar for contract administration purposes. That is a lot easier when the contract requires an element of work to be completed within a certain number of days.


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