The Origins of Our Modern Calendar
The Origins of Our Modern Calendar

by Linda Kerr

Early Calendars
The word calendar is derived from the latin calendarium, meaning an interest or account book, and is related to the Latin word kalend, meaning "I cry!" (Irwin, viii) The town crier of ancient Rome used this expression when he announced the beginning of the months, the market days, and the day near the middle of the month (the Ides of the month). This was necessary because the Romans began each month with the appearance of the new moon. From their "moon-time" of one new moon to the next comes the word moonth - month. (Irwin, viii) The first day of the Roman month became known as the Calends, the day on which the priests called the people together to announce to them sacred days and festivals to be observed during the month. (Douglas, 679)

The ancient Romans seemed to have kept time by two calendar systems. The calendar of moonlight was used for civil and military purposes, with watchers to note the first appearance of each new moon. The country people of Rome used a calendar more suited to farming, beginning in the Spring on March 25 and consisting of twelve fixed months. These months maintained a fixed position in the year's calendar. (Irwin, 80)

As the soldiers of early Rome were drawn from the small farms, they tended to use the farmers' calendar, blending it with the soldiers' calendar. Here they encountered the difficulty of aligning the lunar year with the solar year. The fixed calendar months did not correspond to the moveable months of the calendar of moonlight; there being sometimes 12 and sometimes 13 new moons in a year (actually there are 12.368 lunar months in a solar year). (Irwin, 16) Even after numerous, though irregular, adjustments were made, the Roman year still did not correspond with the solar year, and slipped out of position.

By the time of Julius Caesar (63 B.C.), there was a discrepancy of about three months between the actual spring equinox and the calendar equinox. (Douglas, 679) He therefore established a new Roman calendar to replace the old one, which had been in use since about 753 B.C. (Irwin, 79) Caesar decreed that the calendar year should correspond with the solar year and fixed its length at 365 days, with an extra day every fourth year, for a total length of 365.25 days. The first Julian year was 46 B.C. (Douglas, 679)

The new calendar was a modified version of the calendar of Thoth. Caesar had studied this Egyptian calendar, which had been developed about 3000 B.C., during his military campaign there. It was remarkably simple (in comparison to the old Roman calendar, especially), with the only correction being that which we call the "leap year."

However, the true length of the solar year is 365.2422 days, instead of 365.25 days. The difference is only 11 minutes and 14 seconds, but in 125 years, this amounted to a whole day. (Irwin, 95) The Egyptian priests had discovered this in their thousands of years of record keeping, and allowed for it by omitting a leap year every 125 years. Either Caesar wasn't told about this small but essential fact by his astronomers, or thought it unimportant. Yet after 1000 years the error was 8 days. (Irwin, 96)

The Gregorian Adjustment
By the sixteenth century the error in the Julian calendar amounted to 10 days. In 325 A.D., the spring equinox had fallen on March 21. By 1582 A.D., 1,257 years later, it was on March 11. (Actually, by my calculations, if the error had accrued since 46 B.C., it would be 12 or 13 days instead of only 10. Possibly the spring equinox in Caesar's day was marked on March 24 or 25, the beginning of their year. The 2 or 3 days error between then and 325 A.D. may not be accounted for because by the solar year, the equinox should fall on March 21, which it did in 325 A.D. Also, the Julian calendar was adopted later (3rd to 6th century A.D.) by most other western European countries. The 10-day error may have only been counted back to this late adoption. At any rate, our modern calendar is correct for the spring equinox.)

To compensate for this error and prevent its recurrence, Pope Gregory XIII made what is called the Gregorian Adjustment. He decreed that every year divisible by four (every fourth year) should be a leap year; except the years beginning the centuries, which should have the extra day only when evenly divisible by 400 (this had the same result as omitting a leap year every 125 years. The remaining error would only be one day in about 3,000 years). (Irwin, 95) He also took this time to move the beginning of the year from March 25 to January 1.

To correct the 10-day error that had developed, those days were to be dropped from the calendar. When the adjustment was put into effect in October, 1582, October 4 was followed the next day by October 15.

Not everyone was quick to embrace the new calendar system. The Catholic countries of Spain and Portugal, and parts of Italy, adopted the Gregorian Adjustment on the same day as Rome. It was adopted by the Catholic states of Germany the following year, and in France at about the same time. The Protestant German states did not adopt it until 1700.

"In Great Britain and in her American Colonies, where there was objection to everything originating in Rome, the old calendar, with the new year beginning on March 25th, was used. Because of the confusion arising from the use of a different calendar from that used on the Continent, the British Parliament passed an act in 1750 adopting the Gregorian calendar." (Douglas, 679) By then, since 1700 was a leap year by the Julian Calendar, but not by the adjusted calendar, there were 11 days to be eliminated. The day following September 2, 1752 was to be followed the next day by September 14, "not only in Great Britain but in her American colonies as well. In the course of time the dates of events prior to 1752 were changed to correspond to the new calendar." (Douglas, 679) In accordance with the Gregorian Adjustment, the beginning of the year was moved from March 25, which had been New Year's Day in England and the Colonies, to January 1, the time of the year's beginning in the other countries of Western Europe. (Irwin, 97)

Reactions to the Calendar Change
In 1582 and again in 1752, the change in the calendar gave rise to considerable controversy, including near-riots by simple folk who thought they were being robbed of 11 days of their lives. Debtors found their loans coming due before they were prepared to pay them. Workers hired by the month or half-year demanded to be paid for the lost days; shopkeepers refused to pay for work not done. Nobody was happy. (Irwin, 97)

There was also great confusion over the dates of certain traditional events and holidays, especially Christmas and the wassailing of the apple trees on Twelfth Night. "Seeking a sign, great crowds gathered at Glastonbury at Christmas (new date) 1752, to see what the sacred thorn would do. Local tradition asserted that the thorn was a descendant of one that had sprung from the staff of Joseph of Arimathea when he brought the Christian gospel to Somerset within a few decades of the Crucifixion. It had the reputation of always coming into bloom on Christmas Day, and indeed, in 1645 a clergyman, Rev. John Eachard, quoted the fact as proof that 25 December was Christ's birthday. So the crowds assembled to see whether the thorn would adapt itself to the new calendar.

It did not. No blossoms appeared till 5 January the appointed time by the old style of reckoning." (Whitlock, 13) As a result, when the flowers failed to appear the people refused to accept the new calendar. Hence the proper date of Twelfth Night remains January 17 (old style), as opposed to January 6, New Style. (Whitlock, 13)

A certain American, just before the date on which the adjustment would go into effect, wrote half-jokingly: "Be not astonished, nor look with scorn, dear reader, at such a deduction of days, nor regret as for the loss of so much time, but take this for your consolation, that your expenses will appear lighter and your mind be more at ease. And what an indulgence is here, for those who love their pillow to lie down in Peace on the second of this month and not perhaps awake till the morning of the fourteenth." (From Benjamin Franklin's Almanack, quoted by Cowan, 29; Irwin, 98)

Month Names
Our modern month names stem from the ancient Roman months. Originally the Roman calendar had 10 months, the last six of which were numbered. Two months were added by Numa; January at the beginning and February at the end of the year. This order was reversed in 452 B.C. (Douglas, 679) The old Roman month names were (in order): Martius (March), Aprilis (April), Maius (May), Iunius (June), Quintilis (fifth), Sextilis (sixth), September (seventh), October (eighth), November (ninth), December (tenth), Ianuarius (January), Februarius (February). (Irwin, 86)

In 44 B.C., after two years of operation of the new calendar, the name of the fifth month of Quintilis was changed to Julius (July) to honor the name of Julius Caesar, who had been recently assassinated. (Irwin, 87) In the year 8 B.C., during the reign of Augustus, the month of Sextilis was renamed Augustus (August) in honor of the Emperor. (Irwin, 93)

The Seven-Day Week
In the Thoth calendar the year was divided into 12 months of 30 days each, with five days (six in a leap year) tacked onto the end of the year. (Our way of measuring the size of a circle as 360 represented the Egyptian and Chaldean way of indicating the size of the year. The degree symbol was the simple picture of the sun and stood for "day.") These days were not considered part of any month, and were named, instead of numbered as the months were. The names for these days were those of important deities: Osiris, Horus, Set, Isis, and Nephthys. The extra day may have counted as a double day for Nephthys. (Irwin, 38)

The Thoth system was to influence many other calendars, including our own. Moses, after leading the Israelites from Egypt in 1500 B.C., devised a calendar plan based on the Thoth calendar, but built around weeks rather than months. The seventh day of the week was to be a holy day called the Sabbath. Using their 365.25 day calendar, he divided the year into 52 weeks of seven days each, with 1.25 days left over. (Irwin, 57)

The year was to start on the autumn equinox. At the end of the 52 weeks, totaling 364 days, the remaining day, or two days in a leap year, which were not considered part of any week, would be used as a time of celebration. (Irwin, 59)

No priestly reminders were needed of the Sabbaths, but the priests did have their part to play with the great festival of spring known as the Passover. The Israelites escaped from Egypt at the time of the full moon that came just after the spring equinox. The re-enactment of the various events of that exodus from Egypt, which took the place of the old spring festival, called for the strong light of the full moon to illuminate the area being used. The date of the celebration was established as the first Sabbath after the first full moon after the spring equinox. (Irwin, 61)

As many other cultures did, the Israelites kept time by two calendars: the civil calendar of week days, which was used to note market days, loan dates, and other functions; and the calendar of moonlight, or religious calendar, used for special religious festivals. (Irwin, 61)

Due to the extra day(s) at the end of the 52-week year, both the year and each of the four seasons began on the first day of the week and ended on the last day of the week. The Jews later modified this system by making the extra day(s) a part of the week. As a result, the first year would now begin on the first day of the week, the next year on the second day of the week, the third year on the third day, and so on for common (365 day) years. "After a leap year the starting day jumped over a week day; the third-day beginning of that year, for example, would be followed by a fifth-day beginning for the next year. It was from this leaping-over of a week day that leap year got its name." (Irwin, 93)

After this modification, the Christians had taken over the plan of the seven-day week from the Jews. In 321 A.D. Constantine, having earlier converted to Christianity, signed an act making the seven-day week legal throughout the Roman world. He thereby combined two unlike systems of dividing the year; the seven-day week of the Jews, and the 12 months already in use by the Julian calendar.

The Angles and Saxons of northern and western Europe had a calendar similar to the Egyptian one, with five named days left over at the end of the year. They brought this five-day 'week' to England from across the North Sea about 400 A.D." (Irwin, 107) The Christian missionaries, who were sent out from Rome to convert these "barbarians," added two more names to these five, giving their seven-day week the weekday names we still use today.

These week names are Anglicized versions of important deities among the Norse, Gothic, and Germanic groups:

Tuesday - Tiwsday or Tiwesdaeg. Tyr, god of war ("daeg" means day).
Wednesday - Wodensday or Wodnesdaeg. Norse god Odin, or Wodin. Tyr's father.
Thursday - Thorsday or Thunresdaeg. Thor, Norse god of Thunder.
Friday - Frigsday or Frigedaeg. Norse goddess Freya. Wife of Odin, mother of Thor. Named a day after her lest she be jealous and work evil upon them.
Saturday - Seternesday or Saterdaeg. Norse god Seterne; also the Roman god Saturn who presided over the sowing of the seed. His festival was Saturnalia, December 17. Because of the wildness of the revels during the festival the name has come to mean a time of wild revelry and tumult. (Douglas, 681-682)

The two days added by the missionaries were:

Sunday - Sunnandaeg, from "sunnan" meaning sun. It is regarded as a name surviving from ancient sun worship. As the Resurrection of Christ occurred on the first day of the week the early Christians began to assemble for worship on that day instead of on the Jewish Sabbath, which is Saturday.
Monday - Monandaeg or Moonday. The moon was worshipped as the wife of the sun, among other things. (Douglas, 681)

"The Anglo-Saxon names matched in nature and order those of the Egyptian deities whose names were used by Thoth for his five "extra" days at the year's end. They also matched the names of deities that the Chaldeans gave to those same five days of the calendar they adopted from Egypt." (Irwin, 108)

Egypt: Osiris, Horus, Set, Isis, Nephthys
Chaldea: Nergal, Nabu, Marduk, Ishtar, Ninib
Rome: Mars, Mercury, Jupiter, Venus, Saturn
Anglo-Saxon: Tiw, Woden, Thor, Frig, Seterne

Why did the Anglo-Saxon names match the names of the other times and cultures? One possible explanation is that the Egyptian calendar came to north-central Europe at an early his torical time. In addition, weight and measure systems were similar to those of Egypt; all of these probably came to Europe with Phoenicians trading at Black Sea ports about 1000 B.C. The Norseman's calendar was identical to that of Egypt, except that the year began in midwinter rather than in autumn. (Irwin, 109-110)

"As I gather up the pages I have written, the calendar on the wall reminds me in its printed way that it is
I know that when this May comes the sun overhead will be where it was on the first day of May a year ago, or a hundred years ago. It will rise in the east and set in the west at exactly the same minute that it did on the first of May many decades ago. Just an old sun, it would seem, in an old sky, repeating the May days that have come before.
But I know that this May when it comes will be, for the world, a new May, a fresh May, a May that was never duplicated with exactness in any May before. The May of the calendar is predictable, that of nature's actual world is only partially predictable. We can have both Mays in mind when we say, 'May is a wonderful month to enjoy!' " (Irwin, 109-110)


Cowan, H.C., Time and Its Measurement, World Publishing Company, New York, 1958.
Douglas, George William. The American Book of Days. 1948. The H.W. Wilson Co., New York, NY.
Irwin, Keith G. The 365 Days - The Story of Our Calendar. 1964. Thomas Y. Crowell Co., New York, NY.
Franklin, Benjamin. Almanack.
Whitlock, Ralph. A Calendar of Country Customs. 1978. B.T. Batsford Ltd., London.

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