A History of the New Year

A move from March to January

by Borgna Brunner

The celebration of the new year on January 1st is a relatively new phenomenon. The earliest recording of a new year celebration is believed to have been in Mesopotamia, c. 2000 B.C. and was celebrated around the time of the vernal equinox, in mid-March. A variety of other dates tied to the seasons were also used by various ancient cultures. The Egyptians, Phoenicians, and Persians began their new year with the fall equinox, and the Greeks celebrated it on the winter solstice.

Early Roman Calendar: March 1st Rings in the New Year

The early Roman calendar designated March 1 as the new year. The calendar had just ten months, beginning with March. That the new year once began with the month of March is still reflected in some of the names of the months. September through December, our ninth through twelfth months, were originally positioned as the seventh through tenth months (septem is Latin for "seven," octo is "eight," novem is "nine," and decem is "ten."

January Joins the Calendar

The first time the new year was celebrated on January 1st was in Rome in 153 B.C. (In fact, the month of January did not even exist until around 700 B.C., when the second king of Rome, Numa Pontilius, added the months of January and February.) The new year was moved from March to January because that was the beginning of the civil year, the month that the two newly elected Roman consulsthe highest officials in the Roman republicbegan their one-year tenure. But this new year date was not always strictly and widely observed, and the new year was still sometimes celebrated on March 1.

Julian Calendar: January 1st Officially Instituted as the New Year

In 46 B.C. Julius Caesar introduced a new, solar-based calendar that was a vast improvement on the ancient Roman calendar, which was a lunar system that had become wildly inaccurate over the years. The Julian calendar decreed that the new year would occur with January 1, and within the Roman world, January 1 became the consistently observed start of the new year.

Middle Ages: January 1st Abolished

In medieval Europe, however, the celebrations accompanying the new year were considered pagan and unchristian like, and in 567 the Council of Tours abolished January 1 as the beginning of the year. At various times and in various places throughout medieval Christian Europe, the new year was celebrated on Dec. 25, the birth of Jesus; March 1; March 25, the Feast of the Annunciation; and Easter.

Gregorian Calendar: January 1st Restored

In 1582, the Gregorian calendar reform restored January 1 as new year's day. Although most Catholic countries adopted the Gregorian calendar almost immediately, it was only gradually adopted among Protestant countries. The British, for example, did not adopt the reformed calendar until 1752. Until then, the British Empire and their American colonies still celebrated the new year in March.

The Curious History of the Gregorian Calendar

Eleven days that never were

by Ben Snowden

September 2, 1752, was a great day in the history of sleep.

That Wednesday evening, millions of British subjects in England and the colonies went peacefully to sleep and did not wake up until twelve days later. Behind this feat of narcoleptic prowess was not some revolutionary hypnotic technique or miraculous pharmaceutical discovered in the West Indies. It was, rather, the British Calendar Act of 1751, which declared the day after Wednesday the second to be Thursday the fourteenth.

Prior to that cataleptic September evening, the official British calendar differed from that of continental Europe by eleven daysthat is, September 2 in London was September 13 in Paris, Lisbon, and Berlin. The discrepancy had sprung from Britain's continued use of the Julian calendar, which had been the official calendar of Europe since its invention by Julius Caesar (after whom it was named) in 45 B.C.

Caesar's calendar, which consisted of eleven months of 30 or 31 days and a 28-day February (extended to 29 days every fourth year), was actually quite accurate: it erred from the real solar calendar by only 11 minutes a year. After centuries, though, even a small inaccuracy like this adds up. By the sixteenth century, it had put the Julian calendar behind the solar one by 10 days.

In 1582, Pope Gregory XIII ordered the advancement of the calendar by 10 days and introduced a new corrective device to curb further error: century years such as 1700 or 1800 would no longer be counted as leap years, unless they were (like 1600 or 2000) divisible by 400.

If somewhat inelegant, this system is undeniably effective, and is still in official use in the United States. The Gregorian calendar year differs from the solar year by only 26 secondsaccurate enough for most mortals, since this only adds up to one day's difference every 3,323 years.

Despite the prudence of Pope Gregory's correction, many Protestant countries, including England, ignored the papal bull. Germany and the Netherlands agreed to adopt the Gregorian calendar in 1698; Russia only accepted it after the revolution of 1918, and Greece waited until 1923 to follow suit. And currently many Orthodox churches still follow the Julian calendar, which now lags 13 days behind the Gregorian.

Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals.

Why So Difficult?

Since their invention, calendars have been used to reckon time in advance, and to fix the occurrence of events like harvests or religious festivals. Ancient peoples tied their calendars to whatever recurring natural phenomena they could most easily observe. In areas with pronounced seasons, annual weather changes usually fixed the calendar; in warmer climates such as Southern Europe, Africa, and the Middle East, the moon was used to mark time.

Unfortunately, the cycles of the sun and moon do not synchronize well. A lunar year (consisting of 12 lunar cycles, or lunations, each 29 days long) is only 354 days, 8 hours long; a solar year lasts about 365 days. After three years, a strict lunar calendar would have diverged from the solar calendar by 33 days, or more than one lunation.

The Muslim calendar is hence the only purely lunar calendar in widespread use today. Its months have no permanent connection to the seasons Muslim religious celebrations, such as Ramadan, may thus occur at any date of the Gregorian calendar.

The phases of the moon have nonetheless remained a popular way to divide the solar year, if only because a 365-day year doesn't exactly lend itself to equal subdivision (the 71-day month has yet to find favor among menologists).

To compensate for the difference in the solar and lunar year, calendar makers introduced the practice of intercalationthe addition of extra days or months to the calendar to make it more accurate. The semilunar Hebrew calendar, consisting of twelve 29- and 30-day months, adds an intercalary month seven times every 19 years (which explains the sometimes confusing drift of Passoverand consequently Easter through April and March).

Despite its widespread use, the Gregorian calendar has a number of weaknesses. It cannot be divided into equal halves or quarters; the number of days per month is haphazard; and months or even years may begin on any day of the week.

Best of All Possible Calendars?

Despite its widespread use, the Gregorian calendar has a number of weaknesses. It cannot be divided into equal halves or quarters; the number of days per month is haphazard; and months or even years may begin on any day of the week. Holidays pegged to specific dates may also fall on any day of the week, and vanishingly few Americans can predict when Thanksgiving will occur next year.

Since Gregory XIII, many other proposals for calendar reform have been made. In the 1840s, philosopher Auguste Comte suggested that the 365th day of each year be a holiday not assigned a day of the week. The generic "Year Day" would allow January 1 to fall on a Sunday every year. Needless to say, this clever solution was not widely embraced.

The French Revolution also saw an attempt at the introduction of a new calendar. On October 5, 1793, the revolutionary convention decreed that the year (starting on September 22, 1792the autumnal equinox, and the day after the proclamation of the new republic) would be divided into 12 months of 30 days, named after corresponding seasonal phenomena (e.g. seed, blossom, harvest).

The remaining five days of the year, called sans-culottides, were feast days. In leap years, the extra day, Revolution Day, was to be added to the end of the year. The Revolutionary calendar had no week; each month was divided into three decades, with every tenth day to be a day of rest. This straightforward calendar, however, perished with the Republic.

Leap Year Explained

Leap years synchronize the calendar year with the solar year

by Ann Marie Imbornoni & Mark Hughes

Why do we need leap year?

The Gregorian calendar, which now serves as the standard calendar for civil use throughout the world, has both common years and leap years. A common year has 365 days and a leap year 366 days, with the extra, or intercalary, day designated as February 29. A leap year occurs every four years to help synchronize the calendar year with the solar year, or the length of time it takes the earth to complete its orbit about the sun, which is about 365 days.

The length of the solar year, however, is slightly less than 365 daysby about 11 minutes. To compensate for this discrepancy, the leap year is omitted three times every four hundred years.

In other words, a century year cannot be a leap year unless it is divisible by 400. Thus 1700, 1800, and 1900 were not leap years, but 1600, 2000, and 2400 are leap years.

What are your chances of being born on leap day?

About 1 in 1,500.

When is the birthday party?

If you are born on a Leap Year, do you get your driver's license on February 28th or March 1st? It is an ambiguous question that is decided by each state. Most states, however, consider March 1st the official day. For instance, the Michigan Vehicle Code states that people born on February 29th "are deemed to have been born on March 1st."

How many people were born on leap day?

There are about 187,000 people in the US and 4 million people in the world who were born on Leap Day.

The rules for determining a leap year

Most years that can be divided evenly by 4 are leap years. Exception: Century years are NOT leap years UNLESS they can be evenly divided by 400.

When did leap year originate?

The Gregorian calendar is closely based on the Julian calendar, which was introduced by Julius Caesar in 45 BC. The Julian calendar featured a 12-month, 365-day year, with an intercalary day inserted every fourth year at the end of February to make an average year of 365.25 days. But because the length of the solar year is actually 365.242216 days, the Julian year was too long by .0078 days (11 minutes 14 seconds).

This may not seem like a lot, but over the course of centuries it added up, until in the 16th century, the vernal equinox was falling around March 11 instead of March 21. In 1582, Pope Gregory XIII adjusted the calendar by moving the date ahead by 11 days and by instituting the exception to the rule for leap years. This new rule, whereby a century year is a leap year only if divisible by 400, is the sole feature that distinguishes the Gregorian calendar from the Julian calendar.

Following the Gregorian reform, the average length of the year was 365.2425 days, an even closer approximation to the solar year. At this rate, it will take more than 3,000 years for the Gregorian calendar to gain one extra day in error.

The Ides of March

Just one of a dozen Ides that occur every month of the year

by Borgna Brunner

The soothsayer's warning to Julius Caesar, "Beware the Ides of March," has forever imbued that date with a sense of foreboding. But in Roman times the expression "Ides of March" did not necessarily evoke a dark moodit was simply the standard way of saying "March 15." Surely such a fanciful expression must signify something more than merely another day of the year? Not so. Even in Shakespeare's time, sixteen centuries later, audiences attending his play Julius Caesar wouldn't have blinked twice upon hearing the date called the Ides.

The term Ides comes from the earliest Roman calendar, which is said to have been devised by Romulus, the mythical founder of Rome. Whether it was Romulus or not, the inventor of this calendar had a penchant for complexity. The Roman calendar organized its months around three days, each of which served as a reference point for counting the other days:

Kalends (1st day of the month)

Nones (the 7th day in March, May, July, and October; the 5th in the other months)

Ides (the 15th day in March, May, July, and October; the 13th in the other months)

The remaining, unnamed days of the month were identified by counting backwards from the Kalends, Nones, or the Ides. For example, March 3 would be V Nones5 days before the Nones (the Roman method of counting days was inclusive; in other words, the Nones would be counted as one of the 5 days).

Days in March

March 1: Kalends;March 2: VI Nones;March 3: V Nones;March 4: IV Nones;March 5: III Nones;March 6: Pridie Nones (Latin for "on the day before");March 7: Nones;March 15: Ides

Used in the first Roman calendar as well as in the Julian calendar (established by Julius Caesar in 45 B.C.E.) the confusing system of Kalends, Nones, and Ides continued to be used to varying degrees throughout the Middle Ages and into the Renaissance.

So, the Ides of March is just one of a dozen Ides that occur every month of the year. Kalends, the word from which calendar is derived, is another exotic-sounding term with a mundane meaning. Kalendrium means account book in Latin: Kalend, the first of the month, was in Roman times as it is now, the date on which bills are due.

April Fools' Day: Origin and History

The uncertain origins of a foolish day

by David Johnson and Shmuel Ross

April Fools' Day, sometimes called All Fools' Day, is one of the most light-hearted days of the year. Its origins are uncertain. Some see it as a celebration related to the turn of the seasons, while others believe it stems from the adoption of a new calendar.

New Year's Day Moves

Ancient cultures, including those of the Romans and Hindus, celebrated New Year's Day on or around April 1. It closely follows the vernal equinox (March 20th or March 21st.) In medieval times, much of Europe celebrated March 25, the Feast of Annunciation, as the beginning of the new year.

In 1582, Pope Gregory XIII ordered a new calendar (the Gregorian Calendar) to replace the old Julian Calendar. The new calendar called for New Year's Day to be celebrated Jan. 1. That year, France adopted the reformed calendar and shifted New Year's day to Jan. 1. According to a popular explanation, many people either refused to accept the new date, or did not learn about it, and continued to celebrate New Year's Day on April 1. Other people began to make fun of these traditionalists, sending them on "fool's errands" or trying to trick them into believing something false. Eventually, the practice spread throughout Europe.

Problems With This Explanation

There are at least two difficulties with this explanation. The first is that it doesn't fully account for the spread of April Fools' Day to other European countries. The Gregorian calendar was not adopted by England until 1752, for example, but April Fools' Day was already well established there by that point. The second is that we have no direct historical evidence for this explanation, only conjecture, and that conjecture appears to have been made more recently.

Constantine and Kugel

Another explanation of the origins of April Fools' Day was provided by Joseph Boskin, a professor of history at Boston University. He explained that the practice began during the reign of Constantine, when a group of court jesters and fools told the Roman emperor that they could do a better job of running the empire. Constantine, amused, allowed a jester named Kugel to be king for one day. Kugel passed an edict calling for absurdity on that day, and the custom became an annual event.

"In a way," explained Prof. Boskin, "it was a very serious day. In those times fools were really wise men. It was the role of jesters to put things in perspective with humor."

This explanation was brought to the public's attention in an Associated Press article printed by many newspapers in 1983. There was only one catch: Boskin made the whole thing up. It took a couple of weeks for the AP to realize that they'd been victims of an April Fools' joke themselves.

Spring Fever

It is worth noting that many different cultures have had days of foolishness around the start of April, give or take a couple of weeks. The Romans had a festival named Hilaria on March 25, rejoicing in the resurrection of Attis. The Hindu calendar has Holi, and the Jewish calendar has Purim. Perhaps there's something about the time of year, with its turn from winter to spring, that lends itself to lighthearted celebrations.

Observances Around the World

April Fools' Day is observed throughout the Western world. Practices include sending someone on a "fool's errand," looking for things that don't exist; playing pranks; and trying to get people to believe ridiculous things.

The French call April 1 Poisson d'Avril, or "April Fish." French children sometimes tape a picture of a fish on the back of their schoolmates, crying "Poisson d'Avril" when the prank is discovered.

AugustHistory of the Month's Origin

A history of the month's name

by Borgna Brunner

'July' is for Julius

The Roman Senate named the month of July after Julius Caesar to honor him for reforming their calendar, which had degenerated into a chaotic embarrassment. Bad calculations caused the months to drift wildly across the seasonsJanuary, for example, had begun to fall in the autumn.

The high priest in charge of the calendar, the pontifex maximus, had become so corrupt that he sometimes lengthened the year to keep certain officials in office or abbreviated it to shorten an enemy's tenure.

Effective January 1, 45 B.C.

The new calendar went into effect on the first day of January 709 A.U.C. (ab urbe condita"from the founding of the city [Rome]")January 1, 45 B.C.and put an end to the arbitrary and inaccurate nature of the early Roman system. The Julian calendar became the predominant calendar throughout Europe for the next 1600 years until Pope Gregory made further reforms in 1582.

Certain countries and institutions in fact adhered to this ancient system until well into the twentieth century: the Julian calendar was used in Russia until 1917 and in China until 1949, and to this day the Eastern Orthodox church adheres to Caesar's calendar.

The month Julius replaced Quintilis (quintus = five)the fifth month in the early Roman calendar, which began with March before the Julian calendar instituted January as the start of the year. Unfortunately, Caesar himself was only able to enjoy one July during his lifethe very first July, in 45 B.C. The following year he was murdered on the Ides of March.

Augustus for 'August'

After Julius's grandnephew Augustus defeated Marc Antony and Cleopatra, and became emperor of Rome, the Roman Senate decided that he too should have a month named after him. The month Sextillus (sex = six) was chosen for Augustus, and the senate justified its actions in the following resolution:

Whereas the Emperor Augustus Caesar, in the month of Sextillis . . . thrice entered the city in triumph . . . and in the same month Egypt was brought under the authority of the Roman people, and in the same month an end was put to the civil wars; and whereas for these reasons the said month is, and has been, most fortunate to this empire, it is hereby decreed by the senate that the said month shall be called Augustus.

Not only did the Senate name a month after Augustus, but it decided that since Julius's month, July, had 31 days, Augustus's month should equal it: under the Julian calendar, the months alternated evenly between 30 and 31 days (with the exception of February), which made August 30 days long. So, instead of August having a mere 30 days, it was lengthened to 31, preventing anyone from claiming that Emperor Augustus was saddled with an inferior month.

To accommodate this change two other calendrical adjustments were necessary:

The extra day needed to inflate the importance of August was taken from February, which originally had 29 days (30 in a leap year), and was now reduced to 28 days (29 in a leap year).

Since the months evenly alternated between 30 and 31 days, adding the extra day to August meant that July, August, and September would all have 31 days. So to avoid three long months in a row, the lengths of the last four months were switched around, giving us 30 days in September, April, June, and November.

Among Roman rulers, only Julius and Augustus permanently had months named after themthough this wasn't for lack of trying on the part of later emperors. For a time, May was changed to Claudius and the infamous Nero instituted Neronius for April. But these changes were ephemeral, and only Julius and Augustus have had two-millenia-worth of staying power.

The Names of the Months

See also Greek and Roman Mythology

January: named after Janus, the god of doors and gates

February: named after Februalia, a time period when sacrifices were made to atone for sins

March: named after Mars, the god of war

April: from aperire, Latin for to open (buds)

May: named after Maia, the goddess of growth of plants

June: from junius, Latin for the goddess Juno

July: named after Julius Caesar in 44 B.C.

August: named after Augustus Caesar in 8 B.C.

September: from septem, Latin for seven

October: from octo, Latin for eight

November: from novem, Latin for nine

December: from decem, Latin for ten

NOTE: The earliest Latin calendar was a 10-month one, beginning with March; thus, September was the seventh month, October, the eighth, etc. July was originally called Quintilis, meaning fifth; August was originally called Sextilis, meaning sixth.

The Names of the Days of the Week

See also Greek and Roman Mythology and Norse Mythology

Latin

Old English

English

German

French

Italian

Spanish

Dies Solis

Sunnandaeg

Sunday

Sonntag

dimanche

domenica

domingo

Dies Lunae

Monandaeg

Monday

Montag

lundi

luned

lunes

Dies Martis

Tiwesdaeg

Tuesday

Dienstag

mardi

marted

martes

Dies Mercurii

Wodnesdaeg

Wednesday

Mittwoch

mercredi

mercoled

mircoles

Dies Jovis

Thunresdaeg

Thursday

Donnerstag

jeudi

gioved

jueves

Dies Veneris

Frigedaeg

Friday

Freitag

vendredi

venerd

viernes

Dies Saturni

Saeternesdaeg

Saturday

Samstag

samedi

sabato

sbado

NOTE: The seven-day week originated in ancient Mesopotamia and became part of the Roman calendar in A.D. 321. The names of the days are based on the seven celestial bodies (the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn), believed at that time to revolve around Earth and influence its events. Most of Western Europe adopted the Roman nomenclature. The Germanic languages substituted Germanic equivalents for the names of four of the Roman gods: Tiw, the god of war, replaced Mars; Woden, the god of wisdom, replaced Mercury; Thor, the god of thunder, replaced Jupiter; and Frigg, the goddess of love, replaced Venus.

Note: The first year recorded by this calendar is 1583, the first full year of the Gregorian calendar. 1753 was the first full year in which the U.S. (then a British colony) began using the Gregorian calendar.

Time Measurement, Time Zones, and the International Date Line

The two natural cycles on which time measurements are based are the year and the day. The year is defined as the time required for Earth to complete one revolution around the Sun, while the day is the time required for Earth to complete one turn upon its axis. Earth needs 365 days plus about 6 hours to go around the Sun once, so a year does not consist of a round number of days; the fractional day has to be taken care of by an extra day every fourth year.

But because Earth, while turning upon its axis, also moves around the Sun, there are two kinds of days. A day may be defined as the interval between the highest point of the Sun in the sky on two successive days. This, averaged out over the year, produces the customary 24-hour day. But one might also define a day as the time interval between the moments when a certain point in the sky, say a conveniently located star, is directly overhead. This is called:

Sidereal time. A sidereal day is the time that it takes the Earth to complete one rotation on its axis so that a particular star can be observed twice at the meridian that runs directly overhead. Because the Earth is moving around the Sun as it rotates on its axis, the sidereal day is about 4 minutes shorter than the solar day, being equivalent to 23 hours, 56 minutes, and 4 seconds in mean solar time. As a result, a star will appear to rise about 4 minutes earlier every night, and different stars will be visible at different times of the year. Astronomers use a point that they call the vernal equinox to determine local sidereal time.

Apparent solar time is the time based directly on the Sun's position in the sky. In ordinary life the day runs from midnight to midnight. It begins when the Sun is invisible by being 12 hours from its zenith. Astronomers use the so-called Julian Day, which runs from noon to noon; the concept was invented by the astronomer Joseph Scaliger, who named it after his father, Julius. To avoid the problems caused by leap-year days and so forth, Scaliger picked a conveniently remote date in the past (4713 B.C.) and suggested just counting days without regard to weeks, months, and years. The reason for having the Julian Day run from noon to noon is the practical one that astronomical observations usually extend across the midnight hour, which would require a change in date if the astronomical day, like the civil day, ran from midnight to midnight.

Mean solar time, rather than apparent solar time, is the basis for local civil and standard time. The mean solar time is based on the position of a fictitious mean sun. The reason why this fictitious sun has to be introduced is the following: Earth turns on its axis regularly; it needs the same number of seconds regardless of the season. But the movement of Earth around the Sun is not regular because Earth's orbit is an ellipse. This has the result (as explained in the section The Seasons) that Earth moves faster in January and slower in July. Though it is Earth that changes velocity, it looks to us as if the Sun does. In January, when Earth moves faster, the apparent movement of the Sun looks faster. The mean sun of time measurements, then, is a sun that moves regularly all year round; the real Sun will be either ahead of or behind the mean sun. The difference between the real Sun and the fictitious mean sun is called the equation of time.

Time zones. But if all clocks were actually set by mean solar time we would be plagued by a welter of time differences that would be correct but a major nuisance. A clock on Long Island, correctly showing mean solar time for its location (this would be local civil time), would be slightly ahead of a clock in Newark, N.J. The Newark clock would be slightly ahead of a clock in Trenton, N.J., which, in turn, would be ahead of a clock in Philadelphia. This condition prevailed until 1884, when a system of standard time was adopted by the International Meridian Conference. Earth's surface was divided into 24 zones. The standard time of each zone is the mean astronomical time of one of 24 meridians, 15 degrees apart, beginning at the Greenwich, England, meridian and extending east and west around the globe to the International Date Line. (This system was actually put into use a year earlier by the railroad companies of the U.S. and Canada, who, until then, had to contend with some 100 conflicting local sun times observed in terminals across the land.)

For practical purposes, this convention is sometimes altered. For example, Alaska, for a time, consisted of four of the eight U.S. time zones: the Pacific standard time zone (east of Juneau) and the 6th (Juneau), 7th (Anchorage), and 8th (Nome) zones, encompassing the 135, 150, and 165 meridians, respectively. In 1983, by act of Congress, the entire state (except the westernmost Aleutians) was united into the 6th zone, Alaska standard time.

The eight U.S. standard time zones are: Atlantic (includes Puerto Rico and the Virgin Islands), eastern, central, mountain, Pacific, Alaska, Hawaii-Aleutian (includes all of Hawaii and those Aleutians west of the Fox Islands), and Samoa standard time.

The Date Line. While the time zones are based on the natural event of the Sun crossing a meridian, the date must be an arbitrary decision. The meridians are traditionally counted from the meridian of the observatory of Greenwich, in England, which is called the zero meridian. The logical place for changing the date is 12 hours, or 180, from Greenwich. Fortunately, the 180th meridian runs mostly through the open Pacific. The Date Line makes a zigzag in the north to incorporate the eastern tip of Siberia into the Siberian time system and then another one to incorporate a number of islands into the Hawaii-Aleutian time zone. In the south there is a similar zigzag for the purpose of tying a number of British-owned islands to the New Zealand time system. Otherwise, the Date Line is the same as 180 from Greenwich. At points to the east of the Date Line the calendar is one day earlier than at points to the west of it. A traveler going eastward across the Date Line from one island to another would not have to reset his watch because he would stay inside the time zone, but it would be the same time of the previous day.

History of the Lunar Calendar

The lunar calendar became the basis of the calendars of the ancient Chinese, Babylonians, Greeks, and Jews

During antiquity the lunar calendar that best approximated a solar-year calendar was based on a 19-year period, with 7 of these 19 years having 13 months. In all, the period contained 235 months. Still using the lunation value of 291/2 days, this made a total of 6,9321/2 days, while 19 solar years added up to 6,939.7 days, a difference of just one week per period and about five weeks per century.

Even the 19-year period required adjustment, but it became the basis of the calendars of the ancient Chinese, Babylonians, Greeks, and Jews. This same calendar was also used by the Arabs, but Muhammad later forbade shifting from 12 months to 13 months, so that the Islamic calendar now has a lunar year of about 354 days. As a result, the months of the Islamic calendar, as well as the Islamic religious festivals, migrate through all the seasons of the year.

History of the Egyptian Calendar

The Egyptian year coincided precisely with the solar year only once every 1,460 years

The ancient Egyptians used a calendar with 12 months of 30 days each, for a total of 360 days per year. About 4000 B.C. they added five extra days at the end of every year to bring it more into line with the solar year.1 These five days became a festival because it was thought to be unlucky to work during that time.

The Egyptians had calculated that the solar year was actually closer to 3651/4 days, but instead of having a single leap day every four years to account for the fractional day (the way we do now), they let the one-quarter day accumulate. After 1,460 solar years, or four periods of 365 years, 1,461 Egyptian years had passed. This means that as the years passed, the Egyptian months fell out of sync with the seasons, so that the summer months eventually fell during winter. Only once every 1,460 years did their calendar year coincide precisely with the solar year.

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

1. The correct figures are lunation: 29 d, 12 h, 44 min, 2.8 sec (29.530585 d); solar year: 365 d, 5 h, 48 min, 46 sec (365.242216 d); 12 lunations: 354 d, 8 h, 48 min, 34 sec (354.3671 d).

History of the Roman (Julian) Calendar

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

When Rome emerged as a world power, the difficulties of making a calendar were well known, but the Romans complicated their lives because of their superstition that even numbers were unlucky. Hence their months were 29 or 31 days long, with the exception of February, which had 28 days. However, four months of 31 days, seven months of 29 days, and one month of 28 days added up to only 355 days. Therefore the Romans invented an extra month called Mercedonius of 22 or 23 days. It was added every second year.

Even with Mercedonius, the Roman calendar eventually became so far off that Julius Caesar, advised by the astronomer Sosigenes, ordered a sweeping reform. 46 B.C. was made 445 days long by imperial decree, bringing the calendar back in step with the seasons. Then the solar year (with the value of 365 days and 6 hours) was made the basis of the calendar. The months were 30 or 31 days in length, and to take care of the 6 hours, every fourth year was made a 366-day year. Moreover, Caesar decreed the year began with the first of January, not with the vernal equinox in late March.

This calendar was named the Julian calendar, after Julius Caesar, and it continues to be used by Eastern Orthodox churches for holiday calculations to this day. However, despite the correction, the Julian calendar is still 111/2 minutes longer than the actual solar year, and after a number of centuries, even 111/2 minutes adds up.

The Gregorian Reform

The Julian calendar is phased out

By the 15th century the Julian calendar had drifted behind the solar calendar by about a week, so that the vernal equinox was falling around March 12 instead of around March 20. Pope Sixtus IV (who reigned from 1471 to 1484) decided that another reform was needed and called the German astronomer Regiomontanus to Rome to advise him. Regiomontanus arrived in 1475, but unfortunately he died shortly afterward, and the pope's plans for reform died with him.

Then in 1545, the Council of Trent authorized Pope Paul III to reform the calendar once more. Most of the mathematical and astronomical work was done by Father Christopher Clavius, S.J. The immediate correction, advised by Father Clavius and ordered by Pope Gregory XIII, was that Thursday, Oct. 4, 1582, was to be the last day of the Julian calendar. The next day would be Friday, Oct. 15. For long-range accuracy, a formula suggested by the Vatican librarian Aloysius Giglio was adopted: every fourth year is a leap year unless it is a century year like 1700 or 1800. Century years can be leap years only when they are divisible by 400 (e.g., 1600 and 2000). This rule eliminates three leap years in four centuries, making the calendar sufficiently accurate.

In spite of the revised leap year rule, an average calendar year is still about 26 seconds longer than the Earth's orbital period. But this discrepancy will need 3,323 years to build up to a single day.

Reform Adopted Gradually

The Gregorian reform was not adopted throughout the West immediately. Most Catholic countries quickly changed to the pope's new calendar in 1582. But Europe's Protestant princes chose to ignore the papal bull and continued with the Julian calendar. It was not until 1700 that the Protestant rulers of Germany and the Netherlands changed to the new calendar. In Great Britain (and its colonies) the shift did not take place until 1752, and in Russia a revolution was needed to introduce the Gregorian calendar in 1918. In Turkey, the Islamic calendar was used until 1926.

A Better Calendar?

Despite its widespread use, the Gregorian calendar has a number of weaknesses. It cannot be divided into equal halves or quarters; the number of days per month is haphazard; and months and years may begin on any day of the week. Holidays pegged to specific dates may also fall on any day of the week, and few Americans can predict when Thanksgiving will occur next year. Since Gregory XIII, many other proposals for calendar reform have been made, but none has been permanently adopted. In the meantime, the Gregorian calendar keeps the calendar dates in reasonable unison with astronomical events.

Adoption of the Gregorian Calendar

The Gregorian reform was not adopted throughout the West immediately

Year

Country

1582

Catholic states of Italy, Portugal, Spain, Belgium, Holland, and Poland

1584

German and Swiss Catholic states

1587

Hungary

1700

German, Swiss, and Dutch Protestant States, Denmark, and Norway

1752

Great Britain and its possessions (including the American colonies)

1873

Japan

1875

Egypt

1918

Russia

1924

Greece

1926

Turkey

1949

China

calendar

Measures of Time

The earth completes its orbit about the sun in 365 days 5 hr 48 min 46 secthe length of the solar year. The moon passes through its phases in about 291/2 days; therefore, 12 lunar months (called a lunar year) amount to more than 354 days 8 hr 48 min. The discrepancy between the years is inescapable, and one of the major problems since early days has been to reconcile and harmonize solar and lunar reckonings. Some peoples have simply recorded time by the lunar cycle, but, as skill in calculation developed, the prevailing calculations generally came to depend upon a combination.

The fact that months and years cannot be divided exactly by days and that the years cannot be easily divided into months has led to the device of intercalation (i.e., the insertion of extra days or months into a calendar to make it more accurate). The simplest form of this is shown in ancient calendars which have series of months alternating between 30 and 29 days, thus arriving at mean months of 291/2 days each. Similarly four years of about 3651/4 days each can be approximated by taking three years of 365 days and a fourth year of 366. This fourth year with its intercalary day is the leap year. If calculations are by the lunar cycle, the surplus of the solar over the lunar year (365 over 354) can be somewhat rectified by adding an intercalary month of 33 days every three years.

Reckoning of day and year was considered necessary by many ancient peoples to determine sacred days, to arrange plans for the future, and to keep some intelligible record of the past. There were, therefore, various efforts to reconcile the count in solar, lunar, and semilunar calendars, from the Egyptians and the Greeks to the Chinese and the Maya. The prevailing modern method of constructing a calendar in the Christian West came originally from the Egyptians, who worked out a formula for the solar year (12 months of 30 days each, five extra days a year, and an extra day every four years) that was to be adopted later by the Romans.

The Early Roman Calendar

In its most primitive form the Roman calendar apparently had 10 months, which were (to use corresponding English terms whenever possible): March (31 days), April (29 days), May (31 days), June (29 days), Quintilis (31 days), Sextilis (29 days), September (29 days), October (31 days), November (29 days), and December (29 days). To fill out the 365 days a number of blank days or occasional intercalary months were used. Later, January (29 days) and February (28 days) were added at the end of the year.

In the time of the early republic the so-called year of Numa was added. The Romans thus arrived at a cycle of four years: the first year and the third year had four months of 31 days, seven of 29, and one, February, of 28; the second year had a February of 23 days and an intercalary month of 27 days; the fourth year had a February of 24 days and an intercalary month. The chief trouble with this system was that in a four-year cycle there were four days too many. What was worse, the pontifex maximus was given the power soon after 200 B.C. to regulate the calendar, and the practice grew of using the intercalations for the promotion of political ends to lengthen or to shorten an official's term.

The Julian Calendar

When Julius Caesar became pontifex maximus, the Roman calendar had been so much abused that January was falling in autumn. At this point the methods of the Egyptian calendar were borrowed for the Roman. Julius Caesar, on the advice of the astronomer Sosigenes, added 90 days to the year 46 B.C. (67 days between November and December, 23 at the end of February). This caused the spring of 45 B.C. to begin in March. To retain this position of the seasons, he changed the length of most of the months: March, May, Quintilis (later named July after Julius Caesar), and October he left as they were; he added 2 days each to January and Sextilis (later named August to honor the Emperor Augustus); February was 28 days long except that in every fourth year a day was inserted between the 23d and the 24th of the month.

In Roman computation three days in the month were used for counting the date. These three were the Kalends (1st day of the month), the Nones (the 7th day in March, May, July, and October, the 5th in the other months), and the Ides (the 15th day in March, May, July, and October, the 13th in the other months). The days were counted before, not after, the Kalends, Nones, and Ides. Thus, Jan. 10 was the fourth day before the Ides of January or the fourth day of the Ides of January, because the Romans counted inclusively. Jan. 25 was the eighth of the Kalends of February, Feb. 3 was the third of the Nones of February. Feb. 23 was the seventh of the Kalends of March and remained so when an intercalary day was inserted every fourth year between it and Feb. 24; hence in a leap year there were two days counted as the sixth of the Kalends of March. The leap year was therefore called bissextile [Lat., = sixth twice]. There is a legend that alterations in the length of the months were made later by Augustus to flatter his own vanity, but there seems to be no foundation for this story.

The Gregorian Calendar

The Julian year is 365 days 6 hr, hence a little too long. Therefore, by the 16th cent. the accumulation of surplus time had displaced the vernal equinox to Mar. 11 from Mar. 21, the date set in the 4th cent. In 1582 Pope Gregory XIII rectified this error. He suppressed 10 days in the year 1582 and ordained that thereafter the years ending in hundreds should not be leap years unless they were divisible by 400. The year 1600 was a leap year under both systems, but 1700, 1800, and 1900 were leap years only in the unreformed calendar. The reform was accepted, immediately in most Roman Catholic countries, more gradually in Protestant countries, and in the Eastern Church the Julian calendar was retained into the 20th cent. The present generally accepted calendar is therefore called Gregorian, though it is only a slight modification of the Julian.

The reform was not accepted in England and the British colonies in America until 1752. By that date the English calendar was 11 days different from that of continental Europe. For the intervening period before the reform was introduced into the English calendar, the Gregorian style is called the New Style (N.S.), and the Julian the Old Style (O.S.). New Style years begin Jan. 1, but Old Style years began usually Mar. 25. Thus Washington's birthday, which is Feb. 22, 1732 (N.S.), was Feb. 11, 1731 (O.S.). To avoid confusion sometimes both styles are given; thus 11 Feb. 1731/22 Feb. 1732.

The Christian Ecclesiastical Calendar

The church calendar with its movable feasts shows an interesting example of a harmony of several different systems. The key is the reconciliation of the seven-day week with the Roman calendar (see week). The resurrection of Jesus has always been traditionally reckoned as having taken place on a Sunday (first day of the week); hence the annual feast celebrating the event, Easter, should fall on a Sunday. The Bible places the Passion with relation to the Passover. Since the Jewish Passover is on the evening of the 14th (eve of the 15th) Nisan (see below), it may fall on any day of the week; hence Easter must fall on a Sunday near the 14th Nisan. In ancient times some Eastern Christians celebrated Easter on the 14th Nisan itself; these were called Quartodecimans [Lat., = fourteenth]. In 325 the First Council of Nicaea determined that Easter should fall on the Sunday following the next full moon after the vernal equinox, the full moon being theoretically the 14th day, and Nisan beginning with a new moon in March. The vernal equinox was considered by the church to fall on Mar. 21. The paschal, or Easter, moon is the full moon, the 14th day of which falls after (but not on) Mar. 21.

Today Easter is calculated according to a system that does not take all factors of the lunar period into consideration, and it nearly always varies somewhat from what it should be according to true astronomical calculation. Several different systems have been used for determining Easter. In the 6th and 7th cent. in England, there was a great dispute between Christians who derived their rite from the Celts and Christians who had been converted as a result of the mission of St. Augustine. The dispute was settled at the Synod of Whitby in favor of the Roman system, which prevailed from that time over the entire West. For a conventional means of computing Easter, see the Anglican Book of Common Prayer.

The Jewish Calendar

The Jewish calendar is today a lunisolar or semilunar calendar, i.e., an adjustment of a lunar calendar to the solar year. The months are Tishri (30), Heshvansometimes also called Marheshvan(29 or 30), Kislev (29 or 30), Tebet (29), Sebat or Shebat (30), Adar (29), Nisan (30), Iyar (29), Sivan (30), Tammuz (29), Ab (30), and Elul (29). The intercalary month of 30 days, Adar II, is added after Adar, Nisan being in ancient times the first month. The intercalation is arranged to take place seven times in 19 years; this is called the Metonic cycle after the Greek astronomer Meton who proposed it about 432 B.C. to express the relation between a lunar and solar year. The common year is referred to as a defective, regular, or perfect year, depending upon whether its length is 353, 354, or 355 days; the leap year may have 383 (defective), 384 (regular), or 385 (perfect) days. The Jewish civil year begins about the autumnal equinox, with the festival of Rosh ha-Shanah (the first of Tishri), which in 1999 fell on Sept. 11, marking the start of the Jewish year 5760.

The Islamic Calendar

The Islamic calendar is the only widely used purely lunar calendar, its year varying from 354 to 355 days. Hence the seasons and months have no connection, and there are about 33 years to every 32 Gregorian years. The months are Muharram (30), Safar (29), 1st Rabia (30), 2d Rabia (29), 1st Jumada (30), 2d Jumada (29), Rajab (30), Shaban (29), Ramadan (the fast, 30), Shawwal (29), Dhu-l-Kada (30), and Dhu-l-Hijja (month of the pilgrimage, 29 or 30). The first day of the Islamic calendar, Muharram 1, A.H. 1, was July 16, 622, in the Western calendar (A.H. [Anno Hegirae = in the year of the Hegira] is used to indicate the Islamic year). Muharram 1, A.H. 1420 was Apr. 17, 1999.

Other Calendars

The old Chinese calendar was devised to have six 60-day cycles, each cycle having 10-day periods and three such periods going to make up a month. By the 5th cent. B.C. the solar year was calculated at 365.2444 solar days and the solar month at 29.53059 days. The difference between solar time and the cycles was adjusted by intercalary months and shorter intercalary periods. The years were arranged in major cycles of 60 years with minor cycles of 5 years each. An interesting calendar is that of the Maya, who used a year of 365 days divided into 18 20-day periods, with a 5-day period at the end. A cycle of 260 days was used to name days. These two recurrent cycles resulted in a great cycle of 52 years. This calendar was carefully calibrated, but the year was never readjusted to the error in its length; instead, the feasts and dates were adjusted to the calendar. The Aztec calendar was very similar. Many attempts have been made to devise new calendars, adjusting the months more regularly to the solar year, discarding the week, making the months equal in length, and the like, but they have never been widely adopted. The most celebrated is the French Revolutionary calendar.

Reckoning the Dates Assigned to Years

The Athenian system of identifying years by archons, the Roman system of identifying them by consuls, and the system of reckoning by the year of the reign of a given king or other ruler offer enormous difficulties, and the establishment of chronology is one of the major problems in ancient and medieval history. (The classic work on chronology is that of the Benedictines, first published in 1750, L'Art de vrifier les dates des faits historiques [the art of verifying the dates of historical acts].) For the method of computing years from a fixed point (e.g., the birth of Jesus and the Hegira), see era. The adoption of such era systems has made computation of time much easier.