1752 Calendar Change - Colonial Records & Topics - LibGuides at Connecticut State Library, Division of Library Development Colonial Records & Topics Calendars The 1752 Calendar Change Today, Americans are used to a calendar with a "year" based the earth's rotation around the sun, with "months" having no relationship to the cycles of the moon and New Years Day falling on January 1. However, that system was not adopted in England and its colonies until 1752. The changes implemented that year have created challenges for historians and genealogists working with early colonial records, since it is sometimes hard to determine whether information was entered according to the then-current English calendar or the "New Style" calendar we use today. Throughout history there have been numerous attempts to convey time in relation to the sun and moon. Even now the Chinese and Islamic calendars are based on the motion of the moon around the earth, rather than the motion of the earth in relation to the sun, and the Jewish calendar links years to the cycle of the sun and months to the cycle of the moon. The Julian Calendar In 45 B.C., Julius Caesar ordered a calendar consisting of twelve months based on a solar year.

This calendar employed a cycle of three years of 365 days, followed by a year of 366 days (leap year). When first implemented, the "Julian Calendar" also moved the beginning of the year from March 1 to January 1. However, following the fall of the Roman Empire in the fifth century, the new year was gradually realigned to coincide with Christian festivals until by the seventh century, Christmas Day marked the beginning of the new year in many countries. By the ninth century, parts of southern Europe began observing first day of the new year on March 25 to coincide with Annunciation Day (the church holiday nine months prior to Christmas celebrating the Angel Gabriel's revelation to the Virgin Mary that she was to be the mother of the Messiah). The last day of the year was March 24. However, England did not adopt this change in the beginning of the new year until late in the twelfth century. Because the year began in March, records referring to the "first month" pertain to March; to the second month pertain to April, etc., so that "the 19th of the 12th month" would be February 19.

In fact, in Latin, September means seventh month, October means eighth month, November means ninth month, and December means tenth month. Use of numbers, rather than names, of months was especially prevalent in Quaker records. The Gregorian Calendar During the Middle Ages, it began to became apparent that the Julian leap year formula had overcompensated for the actual length of a solar year, having added an extra day every 128 years. However, no adjustments were made to compensate. By 1582, seasonal equinoxes were falling 10 days "too early," and some church holidays, such as Easter, did not always fall in the proper seasons. In that year, Pope Gregory XIII authorized, and most Roman Catholic countries adopted, the "Gregorian" or "New Style" Calendar." As part of the change, ten days were dropped from the month of October, and the formula for determining leap years was revised so that only years divisible by 400 (e.g., 1600, 2000) at the end of a century would be leap years. January 1 was established as the first day of the new year.

Protestant countries, including England and its colonies, not recognizing the authority of the Pope, continued to use the Julian Calendar. Double Dating Between 1582 and 1752, not only were two calendars in use in Europe (and in European colonies), but two different starts of the year were in use in England. Although the "Legal" year began on March 25, the use of the Gregorian calendar by other European countries led to January 1 becoming commonly celebrated as "New Year's Day" and given as the first day of the year in almanacs. To avoid misinterpretation, both the "Old Style" and "New Style" year was often used in English and colonial records for dates falling between the new New Year (January 1) and old New Year (March 25), a system known as "double dating." Such dates are usually identified by a slash mark [/] breaking the "Old Style" and "New Style" year, for example, March 19, 1631/2. Occasionally, writers would express the double date with a hyphen, for example, March 19, 1631-32.

In general, double dating was more common in civil than church and ecclesiastical records. Changes of 1752 In accordance with a 1750 act of Parliament, England and its colonies changed calendars in 1752. By that time, the discrepancy between a solar year and the Julian Calendar had grown by an additional day, so that the calendar used in England and its colonies was 11 days out-of-sync with the Gregorian Calendar in use in most other parts of Europe. England's calendar change included three major components. The Julian Calendar was replaced by the Gregorian Calendar, changing the formula for calculating leap years. The beginning of the legal new year was moved from March 25 to January 1. Finally, 11 days were dropped from the month of September 1752.

The changeover involved a series of steps: December 31, 1750 was followed by January 1, 1750 (under the "Old Style" calendar, December was the 10th month and January the 11th) March 24, 1750 was followed by March 25, 1751 (March 25 was the first day of the "Old Style" year) December 31, 1751 was followed by January 1, 1752 (the switch from March 25 to January 1 as the first day of the year) September 2, 1752 was followed by September 14, 1752 (drop of 11 days to conform to the Gregorian calendar) Which Calendar Is It? Out of context, it is sometimes hard to determine whether information in colonial records was entered "Old Style" or "New Style." Some examples: In the Public Records of the Colony of Connecticut, "A Corte at New Towne [Hartford] 27 Decr. 1636" is immediately followed by a court held "21 Febr.

1636," which is followed, in turn, by "A Cort att Hartford, Mrch 28th, 1637". Although it may first appear that the February session was entered out of sequence, the arrangement is actually correct. Under the "Old Style" calendar and legal new year, 1636 began on March 25. December 1636 was followed by January 1636 and February 1636, and 1636 continued through March 24. The "Warwick Patent" is dated the "Nineteenth day of March in the Seventh/ yeare of ye reigne of our Sovergne Lord Charles by ye grace of God/ Kinge of England Scotland Ffrance and/ Ireland defender of ye ffaith &c Anno Dom/ 1631." Although not double dated, the historical context indicates that the date as recorded was "Old Style." If double dated, it would have been recorded as March 19, 1631/2; if recorded "New Style," it would be March 19, 1632.

John and Joane Carrington, accused of "familliarity with Sathan the great Enemye of God and mankinde" were indicted by Connecticut's Particular Court on "6 March 1650/1." In his "diary" or notebook, Matthew Grant records that they were executed "mar. 19.50." Although Grant did not employ the double date, had he done so it would have been recorded as March 19, 1650/1. Although current historical scholarship calls for retention of Old Style dates in transcriptions, historians and genealogists need to be aware that some people living at the time converted the date of an event, such as a birthday, from Old Style to New Style. George Washington, for example, was born on February 11, 1731 under the Julian Calendar, but afterwards recognized the date February 22, 1732 to reflect the Gregorian Calendar. Old Christmas Day and the Lost 11 Days Back to Facts of the Day Calendar UK Calendar dates british festivals .... folklore ... anniversaries .... on this day Old Christmas Day and the Lost 11 Days Did you know?

Nothing whatsoever happened in British history between 3 and 13 September 1752. The Gregorian calendar The Gregorian calendar is the one most used nowadays. It is named after Pope Gregory Xlll who introduced it in 1582. There is a leap year every four years (or more precisely, 97 leap years every 400 years). This means that the year corresponds closely with the astronomical year (365.24219 days) so that it is just one day out every 3,300 years. The Julian Calendar Up until 1753, the calendar we used in Britain was the Julian Calendar. It was based on the solar year, the time it takes for the Earth to rotate around the Sun, and thus was less accurate than the Gregorian Calendar. The Julian Calendar was 365.25 days long, which was fractionally too long, and the calendar over time fell out of line with the seasons. All change - "Give us back our 11 days!" In 1752 Britain decided to correct this by abandoning the Julian calendar in favour of the Gregorian.

By doing so, 3 September instantly became 14 September - and as a result, nothing whatsoever happened in British history between 3 and 13 September 1752. Many people thought that the government had stolen eleven days of their lives. They protested in the streets, demanding "Give us back our 11 days!" All change for Christmas! Before the calendar was changed, England celebrated Christmas on the equivalent of the 6th of January by our modern, Gregorian reckoning. That is why in some people still call the 6th January, Old Christmas Day. 6 January is also known as Epiphany or Twelfth Day nrich.maths.org/164 Also on this day ... 6 January 1066: The coronation of Harold II, as King of England, succeeding Edward the Confessor. He reigned for ten months before he died at the Battle of Hastings. 6 January 1540: Henry VIII married Anne of Cleves at Greenwich Palace, London. How long did they stay married? What number wife was Anne? Find the answers here 6 January 1412: The birth of St Joan of Arc, the Maid of Orléans.

She was a great heroine of French history and believed that she had a divine mission to drive the British from France. She died at the stake after being captured by the Burgundians and sold to the British. 6 January 1540: King Henry VIII married Anne of Cleves, his fourth wife. 6 January 1916: World War I - The British Government introduced conscription, to replace the many thousands killed in the trenches in France. 6 - 7 January 1928: Four people were drowned, and many paintings in the basement of the Tate Gallery were severely damaged, when the Thames flooded. The water was deep enough to fill the moat of the Tower of London. 6 January 1999: Prince Edward & Sophie Rhys-Jones announced their engagement. Links Calendar Reform in England, 1752 Calendar Reform in England, 1752 It is widely known that in September 1752, Great Britain switched from the Julian Calendar to the Gregorian Calendar. In order to achieve the change, 11 days were 'omitted' from the calendar - i.e.

the day after 2 September 1752 was 14 September 1752. This change was as a result of an Act of Parliament - the "Calendar Act" of 1751 An Act for Regulating the Commencement of the Year; and for Correcting the Calendar now in Use. What isn't so widely known is a second change which the Act introduced - as named in the first part of the Act's title. The Act changed the first day of the year (or, if you want to impress your friends with a new word, the Supputation of the Year). Prior to 1752 in England, the year began on 25 March (Lady Day). Lady Day is one of the Quarter Days, which are still used in legal circles. The Quarter Days divide the year in quarters (hence the name :-), and the Quarter Days are: Lady Day (25 March), Midsummers Day (24 June), Michaelmas Day (29 September), and Christmas Day (25 December). So, in England, the day after 24 March 1642 was 25 March 1643.

The Act changed this, so that the day after 31 December 1751 was 1 January 1752. As a consequence, 1751 was a short year - it ran only from 25 March to 31 December. To throw some more confusion on the issue, Scotland had changed the first day of the year to 1 January in 1600 (in 1600, Scotland was a separate kingdom). When King James VI of Scotland became also King James I of England in 1603, the possibilities of date confusion must have been very large. Historians have to be on their toes with dates prior to 1752. For example, in The Tower of London there is some graffiti scratched into a cell wall by someone imprisoned in January 1642 for his role in the Battle of Edgehill (which took place on 23 October 1642). Some unanswered questions There is considerable evidence of contemporary dual dating. For example, some essentially contemporary paintings of the execution of King Charles I on Tuesday 30 January 1648 have a title bearing the date 30 January 1648/9.

Samuel Pepys's diary begins on New Years Day (1 January) 1660, but it is clear that this is actually the year 1659/60. So was the Calendar Act in 1751 merely formalising common usage, or was it a radical change ? The preface to one modern book of Samuel Pepys's diary states that using 1 January as the start of the year was common practice at that time - i.e. 1660. I've seen a pamphlet at Broughton Castle which refers to a speech made on Thursday 27 January 1658 - and the pamphlet states it was printed in 1659. In order for the day to be a Thursday, this must be referring to 27 January 1658/9 (i.e. the pamphlet was printed some months after the speech), however the year is specified as 1658 - and not as 1658/9. So the year was commencing on 25 March in 1658, but on 1 January in 1660 ?

Perhaps the answer is connected with the coronation of King Charles II in Scotland on 1 January 1651 - that's a Scottish date, for a Scottish king. Perhaps the Royalist cause used 'Scottish' dates, and the Parliamentarian cause used 'old style' dates ? Although this theory maybe doesn't sit well with the fact that from 1654 Pepys had been steward to Edward Mountagu, a General-at-Sea in Cromwell's Protectorate... King Charles II did not become king of England until 8 May 1660 (coronation on 23 April 1661), after the start of Samuel Pepys's diary. Leap Years in the Julian Calendar In the Julian Calendar, leap years occurred every 4 years, and in leap years the 29 February was added. But remember that 29 February was in the last quarter of the year by the old reckoning. It appears that leap years were those where the year number was one less than an exact multiple of 4!

The House of Commons Journal for Wednesday, February 29th, 1659 would seem to bear this out - remembering that this date is otherwise expressed as 29 February 1659/60, and appears in Samuel Pepys's diary as 29 February 1660 (just to add to the confusion). House of Commons Journal for Thursday, 29 February 1643 (otherwise 29 February 1643/4) and House of Commons Journal for Tuesday, 29 February 1647 (otherwise 29 February 1647/8) confirm this, although note the Latin form of the dates which was presumably dropped in the Commonwealth/Protectorate. The Tax Year Lady Day was one of the days when rents were traditionally due. In fact, this practice must have continued will beyond the 18th century as I've seen paintings of large meals for farm workers on Lady Day. Taxes were also due on Lady Day.

With the 'loss' of 11 days in September 1752 and the stories of riots on the street, people weren't impressed with having to pay their taxes in March 1753 like nothing had happened (in fact, as 25 March 1753 was a Sunday the taxes were due on Monday 26 March 1753 ) - so the taxman skipped the 11 days and decreed that taxes were due on 6 April 1753. And, to this day, the UK tax year starts on 6 April.

The British Switch to the Gregorian Calendar The British Switch to the Gregorian Calendar Newsgroups: soc.genealogy.computing From: edshaw@iglou.com (Edward Shaw) Subject: Gregorian Calendar X-Nntp-Posting-Host: dp2-027.ppp.iglou.com Message-ID: <DFvpK9.CuK@iglou.com> Sender: news@iglou.com (News Administrator) Organization: IgLou Internet Services (1-800-436-4456) X-Newsreader: News Xpress Version 1.0 Beta #2.1 Date: Tue, 3 Oct 1995 15:29:20 GMT THE AMAZING 80% YEAR OF 1752 The modern calendar is a compilation of usages dating from the days of Julius Caesar, when the Greek astronomer and mathematician Sosigenes devised for Rome a calendar only essentially familiar to us as our present-day calendar.

It was during the late 16th century that work of the 6th century Anglo-Saxon monk, Bede, was submitted to Pope Gregory XIII who accepted the calculations and made the decision to issue a more accurate calendar which ultimately was accepted. The Gregorian calendar was adopted by most Roman Catholic countries. Many protestant countries did not accept the new calendar until the 18th century, including Britain ... which meant America as well. The British finally accepted the Gregorian calendar for itself and all its possessions effective March 25, 1752. But, a remarkable 2-step change was made which is little realized today. Read on ... It is most important that the reader understand that the British used to change the year number on March 25th and not January 1st as we do today. On March 24, 1751 the next day would be March 25, 1752 advancing the year as usual. But, a somewhat confusing phenomenon occurred, and for present day imaginations, comprehension requires close attention. First, it was decreed that 1752 should end with December 31st and not be carried on to the next March 25th.

Second, it was also decreed that the arrival of September 2, 1752 should be called September 14, 1752. For the sake of clarity we explain; the period of January 1 -- March 24, 1751 was the end of an epoch. The year of 1752 began on March 25th and ended with December 31, 1752, thus the earlier days of 1752 never existed, as the deleted days of September 2--13 also never existed. The year 1752 was a very short year; 72 days shorter, in fact. Of course, dates may be recomputed from the old to the new calendars. For instance, George Washington's birthday was February 11, 1731 as far as his mother was concerned. Today, we must reckon his birthday as February 22, 1732 in consideration of the new calendar. To put it in perspective, if we count backwards from today the actual number of days since G.W was born, we would come up with February 22, 1732 using the present-day calendar.

To convert from the old Julian to the new Gregorian calendar, one must add 10 to 13 days to the old date, and sometimes change the year one extra when the date considered falls within the period January 1 -- March 24. This is crucially important to those interested in genealogy and historical research. Documented dates before March 25, 1752 do not necessarily always corrobate a stated period of time. And, references to any New Year's Day before 1752, in Great Britain, meant March 25th. It's true ... every syllable of it.

From: Brian Pears <brian@swinhope.demon.co.uk> Newsgroups: soc.genealogy.computing Subject: Re: Gregorian Calendar Date: Wed, 04 Oct 1995 02:25:01 GMT Message-ID: <810342389wnr@swinhope.demon.co.uk> References: <DFvpK9.CuK@iglou.com> Reply-To: brian@swinhope.demon.co.uk X-NNTP-Posting-Host: swinhope.demon.co.uk X-Broken-Date: Wednesday, Oct 04, 1995 02.25.01 X-Newsreader: Newswin Alpha 0.7 In article: <DFvpK9.CuK@iglou.com> edshaw@iglou.com (Edward Shaw) writes: 2. Second, it was also decreed that the arrival of September 2, 1752 should be called September 14, 1752. This should be Wednesday Sept 2 1752 was followed by Thursday Sept 14.

Sept 2 existed, Sept 3--13 (11 days) did not, Sept 14 existed. Remember the slogan of the protestors "Give us back our 11 days". 6 Things You May Not Know About the Gregorian Calendar - History in the Headlines 6 Things You May Not Know About the Gregorian Calendar September 13, 2012 By Jennie Cohen William Hogarth’s painting “An Election Entertainment,” thought to have sparked rumors that English citizens rioted after the adoption of the Gregorian calendar. Share this: 6 Things You May Not Know About the Gregorian Calendar Author 6 Things You May Not Know About the Gregorian Calendar URL Google If you were living in England or one of the American colonies 260 years ago, this date—September 13, 1752—didn’t exist. Neither did the 10 days preceding it. Instead, you would have gone to bed on the evening of September 2 and woken up on the morning of September 14. Eleven days had been effectively skipped over as part of the parliamentary measure that implemented the Gregorian calendar, aligning Britain and its overseas possessions with the rest of Western Europe.

In most of the world today, people continue to track their days, months and years using the centuries-old system, so chances are you’re intimately familiar with its workings. Still, there are a few things about the Gregorian calendar that might come as a surprise. 1. The original goal of the Gregorian calendar was to change the date of Easter. In 1582, when Pope Gregory XIII introduced his Gregorian calendar, Europe adhered to the Julian calendar, first implemented by Julius Caesar in 46 B.C. Since the Roman emperor’s system miscalculated the length of the solar year by 11 minutes, the calendar had since fallen out of sync with the seasons. This concerned Gregory because it meant that Easter, traditionally observed on March 21, fell further away from the spring equinox with each passing year. 2. Leap years don’t really occur every four years in the Gregorian calendar. The Julian calendar included an extra day in February every four years. But Aloysus Lilius, the Italian scientist who developed the system Pope Gregory would unveil in 1582, realized that the addition of so many days made the calendar slightly too long.

He devised a variation that adds leap days in years divisible by four, unless the year is also divisible by 100. If the year is also divisible by 400, a leap day is added regardless. While this formula may sound confusing, it did resolve the lag created by Caesar’s earlier scheme—almost. 3. The Gregorian calendar differs from the solar year by 26 seconds per year. Despite Lilius’ ingenious method for syncing the calendar with the seasons, his system is still off by 26 seconds. As a result, in the years since Gregory introduced his calendar in 1582, a discrepancy of several hours has arisen. By the year 4909, the Gregorian calendar will be a full day ahead of the solar year. 4. Some Protestants viewed the Gregorian calendar as a Catholic plot. Though Pope Gregory’s papal bull reforming the calendar had no power beyond the Catholic Church, Catholic countries—including Spain, Portugal and Italy—swiftly adopted the new system for their civil affairs. European Protestants, however, largely rejected the change because of its ties to the papacy, fearing it was an attempt to silence their movement.

It wasn’t until 1700 that Protestant Germany switched over, and England held out until 1752. Orthodox countries clung to the Julian calendar until even later, and their national churches have never embraced Gregory’s reforms. 5. Britain’s adoption of the Gregorian calendar sparked riots and protest—maybe. According to some accounts, English citizens did not react kindly after an act of Parliament advanced the calendar overnight from September 2 to September 14, 1752. Rioters supposedly took to the streets, demanding that the government “give us our 11 days.” However, most historians now believe that these protests never occurred or were greatly exaggerated. On the other side of the Atlantic, meanwhile, Benjamin Franklin welcomed the change, writing, “It is pleasant for an old man to be able to go to bed on September 2, and not have to get up until September 14.” 6. Before the Gregorian calendar’s adoption, the English new year began on March 25, or Lady Day. Julius Caesar’s calendar reform of 46 B.C. instituted January 1 as the first of the year.

During the Middle Ages, however, European countries replaced it with days that carried greater religious significance, such as December 25 (the anniversary of Jesus’ birth) and March 25 (the Feast of the Annunciation). The latter, known as Lady Day because it celebrates the Virgin Mary, marked the beginning of the year in Britain until January 1, 1752. Tags The Gregorian Calendar Home Calendar Gregorian The Gregorian Calendar The Gregorian calendar is today's internationally accepted civil calendar and is also known as the Western or Christian calendar. The Vatican, 'birth place' of the Gregorian calendar. Rome's Vatican City is the 'birth place' of the Gregorian calendar, named after Pope Gregory XIII, who introduced it. ©iStockphoto.com/Antonio Gravante Go to Calendar 12 Irregular Months The Gregorian Calendar is the most widely used calendar in the world today. It is a solar calendar based on a 365-day common year divided into 12 months of irregular lengths. 11 of the months have either 30 or 31 days , while the second month, February , has only 28 days during the common year.

However, nearly every four years is a leap year , when one extra – or intercalary – day, is added on 29 February , making the leap year in the Gregorian calendar 366 days long. Replaced Julian Calendar The Gregorian calendar's predecessor, the Julian Calendar , was replaced because it was too inaccurate. It did not properly reflect the actual time it takes the Earth to circle once around the Sun, known as a tropical year . Realigned With the Sun The Julian calendar's formula to calculate leap years produced a leap year every four years. This is too often, and eventually the Julian calendar was several days out of sync with the fixed dates for astronomical events like equinoxes and solstices . The introduction of the Gregorian calendar allowed for the realignment with events like the vernal equinox and winter solstice .

New Leap Year Formula The Gregorian calendar was first adopted in Italy, Poland, Portugal and Spain in 1582 , and included the following changes: New formula for calculating leap years: The year is evenly divisible by 4; If the year can be evenly divided by 100, it is NOT a leap year, unless; The year is also evenly divisible by 400: Then it is a leap year 10 days were dropped in October 1582 New rules for calculating Easter -dates Is Any Calendar Perfect? The more advanced leap year formula makes the Gregorian calendar far more accurate than the Julian. However, it is not perfect either. Compared to the tropical year, it is off by one day every 3236 years. Who Designed the Calendar? Although the Gregorian calendar is named after Pope Gregory XIII, it is an adaptation of a calendar designed by Italian doctor, astronomer and philosopher Luigi Lilio (also known as Aloysius Lilius). He was born around 1510 and died in 1576, six years before his calendar was officially introduced. The Julian and Gregorian Calendars The Julian and Gregorian Calendars by Peter Meyer 1.

The Julian Calendar For many European institutions, we can thank the Romans (for good or for bad, though they too had their predecessors in the Greeks, Egyptians and Babylonians). So with the solar calendar currently in widespread use. Originally the Romans numbered years ab urbe condita, that is, "from the founding of the city" (of Rome, where much of the character of the modern world had its beginnings). Had this old calendar remained in use, 1996-01-14 would have been New Year's Day in the year 2749 a.u.c. (In this article dates are often given in IS0 8601 format .) Following his conquest of Egypt in 48 B.C. Julius Caesar consulted the Alexandrian astronomer Sosigenes about calendar reform (since the a.u.c. calendar then used by the Romans was completely inadequate to the needs of the emerging empire, which Caesar was poised to command, briefly as it turned out). The calendar which Julius Caesar adopted in the year 709 a.u.c.

(what we now call 46 B.C.) was identical to the Alexandrian Aristarchus' calendar of 239 B.C., and consisted of a solar year of twelve months and of 365 days with an extra day every fourth year. It is unclear as to where or how Aristarchus arrived at this calendar, but one may speculate that Babylonian science was involved. As we can read in the excellent article, "The Western Calendar and Calendar Reforms" in the Encyclopedia Brittanica, Sosigenes decided that the year known in modern times as 46 B.C. should have two intercalations. The first was the customary intercalation of 23 days following February 23, the second, "to bring the calendar in step with the equinoxes, was achieved by inserting two additional months between the end of November and the beginning of December. This insertion amounted to an addition of 67 days, making a year of no less than 445 days and causing the beginning of March, 45 B.C.

in the Roman republican calendar, to fall on what is still called January 1 of the Julian Calendar." According to Kevin Tobin Julius Caesar wanted to start the year on the vernal equinox or the winter solstice, but the Senate, which traditionally took office on January 1st, the start of the Roman civil calendar year, wanted to keep January 1st as the start of the year, and Caesar yielded in a political compromise. The Roman date-keepers initially misunderstood Caesar's instructions concerning the new calendar (according to Macrobius), and erroneously took every third year, rather than every fourth year, to be a leap year. There is some dispute as to exactly which years from 43 B.C. through to 8 A.D. were actually leap years, but a reconstruction which is consistent with the available evidence is that every third year following 43 B.C. (i.e. 40 B.C., 37 B.C., etc.) was a leap year, until 10 B.C., after which, according to this hypothesis, Augustus Caesar (Julius Caesar's successor) suspended leap years, reinstating them with the leap year of 4 A.D.

Another source of uncertainty regarding exact dating of days at this time derives from changes made by Augustus to the lengths of the months. According to some accounts, originally the month of February had 29 days and in leap years 30 days (unlike 28 and 29 now). It lost a day because at some point the fifth and six months of the old Roman calendar were renamed as Julius and Augustus respectively, in honor of their eponyms, and the number of days in August, previously 30, now became 31 (the same as the number of days in July), so that Augustus Caesar would not be regarded as inferior to Julius Caesar. The extra day needed for August was taken from the end of February. However there is still no certainty regarding these matters, so all dates prior to A.D. 4, when the Julian Calendar finally stabilized, are uncertain. Subsequently the Julian Calendar became widespread as a result of its use throughout the Roman Empire and later by various Christian churches, which inherited many of the institutions of the Roman world. The system of numbering years A.D. (for "Anno Domini") was instituted in about the year 527 A.D.

by the Roman abbot Dionysius Exiguus , who reckoned that the Incarnation of Jesus had occurred on March 25 in the year 754 a.u.c., with his birth occurring nine months later. Thus the year 754 a.u.c. was designated by him as the year 1 A.D. It is generally thought that his estimate of the time of this event was off by a few years (and there is even uncertainty as to whether he identified 1 A.D. with 754 a.u.c. or 753 a.u.c.). The question has been raised as to whether the first Christian millennium should be counted from 1 A.D. or from the year preceding it. According to Dionysius the Incarnation occurred on March 25th of the year preceding 1 A.D. (with the birth of Jesus occurring nine months later on December 25th), so it is reasonable to regard that year, rather than 1 A.D. as the first year of the Christian Era. In that case 1 A.D. is the second year, and 999 A.D.

is the 1000th year, of the first Christian millennium, implying that 1999 A.D. is the final year of the second Christian millennium and 2000 A.D. the first year of the third. 2. The Gregorian Reform The average length of a year in the Julian Calendar is 365.25 days (one additional day being added every four years). This is significantly different from the "real" length of the solar year. However, there is uncertainty among astronomers as to what the length of the solar year really is (see Simon Cassidy's Error in Statement of Tropical Year ). The main competing values seem to be the "mean tropical year" of 365.2422 days ("mean solar days") and the "vernal equinox year" of 365.2424 days. The difference of the length of the Julian calendar year from the length of the real solar year is thus 0.0078 days (11.23 minutes) in the former case and 0.0076 days (10.94 minutes) in the latter case.

Whatever, this error accumulates so that after about 131 years the calendar is out of sync with the equinoxes and solstices by one day. Thus as the centuries passed the Julian Calendar became increasingly inaccurate with respect to the seasons. This was especially troubling to the Roman Catholic Church because it affected the determination of the date of Easter, which, by the 16th Century, was well on the way to slipping into summer. Pope Paul III recruited several astronomers, principally the Jesuit Christopher Clavius (1537-1612), to come up with a solution. They built upon calendar reform proposals by the astronomer and physician Luigi Lilio (d. 1576). When Pope Gregory XIII was elected he found various proposals for calendar reform before him, and decided in favor of that of Clavius. On 1582-02-24 he issued a papal bull, Inter Gravissimas, establishing what is now called the Gregorian Calendar reform.

(The full text may be read in both the Latin original and a French translation by Rudolphe Audette, and in an English translation , recently done by Bill Spencer.) The Gregorian reform consisted of the following: Ten days were omitted from the calendar, and it was decreed that the day following (Thursday) October 4, 1582 (which is October 5, 1582, in the old calendar) would thenceforth be known as (Friday) October 15, 1582. The rule for leap years was changed. In the Julian Calendar a year is a leap year if it is divisible by 4. In the Gregorian Calendar a year is a leap year if either (i) it is divisible by 4 but not by 100 or (ii) it is divisible by 400. In other words, a year which is divisible by 4 is a leap year unless it is divisible by 100 but not by 400 (in which case it is not a leap year).

Thus the years 1600 and 2000 are leap years, but 1700, 1800, 1900 and 2100 are not. New rules for the determination of the date of Easter were adopted. The position of the extra day in a leap year was moved from the day before February 25th to the day following February 28th. According to some, the term "leap year" derives from the fact that the day of the week on which certain festivals were held normally advanced by one day (since 365 = 7*52 + 1), but in years with an extra day the festivals would "leap" to the weekday following that. However, it may be derived from an old Norwegian word "hlaupâr" which entered the English language at the time of the Viking invasions (8th - 10th Centuries).

In his excellent book Marking Time Duncan Steel remarks (p.165) that it is often claimed that part of the Gregorian reform consisted in setting the first day of the year (New Year's Day) to January 1st, but that in fact the papal bull made no reference to the date of New Year's Day. January 1st was already New Year's Day in many European countries. The ecclesiastical New Year coincided with Christmas Day until it was changed to January 1st by Pope Pius X in 1910 (coming into effect in 1911). It may be noted that there was no necessity for ten days, rather than, say, twelve days to have been omitted from the calendar. In fact, the calendar could have been reformed without omitting any days at all, since only the new rule for leap years is required to keep the calendar synchronized with the vernal equinox. The number of days omitted determines the date for the vernal equinox, an omission of ten days resulting in a date usually of March 20th . The vernal equinox year during the last 2000 years is 365.2424 days.

The average length of the Julian year (365.25 days) differs from this value by 0.0076 days. So from the year 1 to the year 1582 the calendar drifted off the vernal equinox year by 1581*0.0076 = 12.02 days. Why didn't Pope Gregory remove twelve days, instead of just ten? It has to do with the First Council of Nicaea, which was held in Nicaea (now Iznik, Turkey) in the year 325 A.D. One of the matters settled by this council was the method for determining the date of Easter (which should occur around the vernal equinox), so as to make it independent of the Jewish Calendar.

From the year 325 to the year 1582 the calendar diverged (from the vernal equinox) by 1257*0.0076 = 9.55 days, so ten days were removed in an attempt to restore the date of the vernal equinox to (about) the same date of the year at which it had occurred at the time of the Council of Nicaea. The matter is not this simple, however, because the date of the vernal equinox in the calendar of the Roman Catholic Church as established by the Council of Nicaea (in 325 A.D.) is March 21, but the effect of removing ten days in 1582 had the result that the vernal equinox occurs in the Gregorian Calendar mostly on March 20, less often on March 21, sometimes on March 19 and sometimes even on March 22 according to local time in the Far East. So should Pope Gregory have omitted nine days? Or perhaps eleven? Presumably Pope Gregory's astronomical advisors considered all three possibilities.

Some say that the choice of ten was a compromise, supported by the fact that the omission of ten days made it easier to correct old calendars simply by the insertion of an "X" (the Latin numeral for "10"). In fact a non-Gregorian calendar reform (involving a 33-year cycle and a prime meridian running through Virginia ) would have stabilized the vernal equinox at March 21 for the whole world (as Simon Cassidy has shown ). Whether Pope Gregory's advisors were aware of this reform option is not known for sure. 3. Adoption of the Gregorian Calendar The Gregorian Calendar was adopted immediately upon the promulgation of Pope Gregory's decree in the Catholic countries of Italy, Spain, Portugal and Poland, and shortly thereafter in France and Luxembourg. During the next year or two most Catholic regions of Germany, Belgium, Switzerland and the Netherlands came on board. Hungary followed in 1587. The rest of the Netherlands, Denmark, Germany and Switzerland made the change during 1699 to 1701.

By the time the British were ready to go along with the rest of Europe, the old calendar had drifted off by one more day, requiring a correction of eleven days, rather than ten. The Gregorian Calendar was adopted in Britain (and in the British colonies) in 1752, with (Wednesday) September 2, 1752, being followed immediately by (Thursday) September 14, 1752. In many countries the Julian Calendar was used by the general population long after the official introduction of the Gregorian Calendar. Thus events were recorded in the 16th to 18th Centuries with various dates, depending on which calendar was used. Dates recorded in the Julian Calendar were marked "O.S." for "Old Style", and those in the Gregorian Calendar were marked "N.S." for "New Style". To complicate matters further New Year's Day, the first day of the new year, was celebrated in different countries, and sometimes by different groups of people within the same country, on either January 1, March 1, March 25 or December 25. January 1 seems to have been the usual date but there was no standard observed.

With the introduction of the Gregorian Calendar in Britain and the colonies New Year's Day was generally observed on January 1. Previously in the colonies it was common for March 24 of one year to be followed by March 25 of the next year. This explains why, with the calendrical reform and the shift of New Year's Day from March 25 back to January 1, the year of George Washington's birth changed from 1731 to 1732. In the Julian Calendar his birthdate is 1731-02-11 but in the Gregorian Calendar it is 1732-02-22. Sweden adopted the Gregorian Calendar in 1753, Japan in 1873, Egypt in 1875, Eastern Europe during 1912 to 1919 and Turkey in 1927. Following the Bolshevik Revolution in Russia it was decreed that thirteen days would be omitted from the calendar, the day following January 31, 1918, O.S. becoming February 14, 1918, N.S.

(Further information can be found in The Perpetual Calendar and here .) In 1923 the Eastern Orthodox Churches adopted a modified form of the Gregorian Calendar in an attempt to render the calendar more accurate (see below). October 1, 1923, in the Julian Calendar became October 14, 1923, in the Eastern Orthodox calendar. The date of Easter is determined by reference to modern lunar astronomy (in contrast to the more approximate lunar model of the Gregorian system). The Gregorian Calendar is the calendar which is currently in use in all European and European-influenced countries, and Dionysius Exiguus's system of numbering years A.D. has endured to the present time. The abbreviation A.D. is short for "Anni Domini Nostri Jesu Christi", i.e., "in the year of Our Lord Jesus Christ". Since Muslims, Jews, etc., may not be entirely comfortable with this, the designation "A.D." is now sometimes replaced by the more neutral C.E. (for "Common Era"), and instead of B.C. ("Before Christ") B.C.E. (for "Before Common Era") is sometimes used. 4.

Astronomical Year Numbering Astronomers designate years prior to 1 A.D. by means of zero and negative numbers, according to the sequence of numbers ..., -2, -1, 0, 1, 2, .... Between the year 1 and the year -1 there occurs the year 0. Thus astronomers adopt the following convention: 1 A.D. = 1 C.E. = year 1 1 B.C. = 1 B.C.E. = year 0 2 B.C. = 2 B.C.E. = year -1 and so on More generally, a year popularly designated n B.C. or n B.C.E. is designated by astronomers as the year -(n-1). The rules for leap years work for years prior to 1 C.E. only if those years are expressed according to the astronomical system, not if expressed as years B.C.E. 4 C.E. is a leap year in both calendars, 1 B.C.E. = astronomical year 0, 5 B.C.E. = year -4, 9 B.C.E. = year -8, and so on, are all leap years. 101 B.C.E.

= year -100 is a leap year in the ( proleptic ) Julian Calendar but not in the (proleptic) Gregorian Calendar. These statements, however, are only theoretically true, because (as noted above) prior to 4 C.E. the leap years were not observed correctly by the Roman calendrical authorities. The choice of which system of numbering years to use is relevant to the question: When Does the New Millennium Begin? as can be seen from the following: Gregorian Religiously Common Era Calendar Neutral Calendar 3 BC 3 BCE -2 CE 2 BC 2 BCE -1 CE CE millennium begins 0-01-01 CE 1 BC 1 BCE 0 CE Gregorian millennium usually taken to begin 1-1-1 AD 1 AD 1 CE 1 CE 2 AD 2 CE 2 CE ... ... ...

1998 AD 1998 CE 1998 CE 1999 AD 1999 CE 1999 CE CE millennium ends 1999-12-31 CE CE millennium begins 2000-01-01 CE 2000 AD 2000 CE 2000 CE Gregorian millennium usually taken to end 2000-12-31 AD Gregorian millennium usually taken to begin 2001-1-1 AD 2001 AD 2001 CE 2001 CE January 1st, 1 AD is usually taken to be the start of the first Christian millennium, but a case could be made for January 1st, 1 BC (see the comment above concerning the Incarnation ), which would imply that the third Christian millennium began on January 1st, 2000 AD. 5.

The Proleptic Julian and Gregorian Calendars Every date recorded in history prior to October 15, 1582 (Gregorian), such as the coronation of Charlemagne as Holy Roman Emperor on Christmas day in the year 800, is a date in the Julian Calendar, since on those dates the Gregorian Calendar had not been invented (or at least, had not been implemented). We can, however, identify particular days prior to October 15, 1582 (Gregorian), by means of dates in the Gregorian Calendar simply by projecting the Gregorian dating system back beyond the time of its implementation. A calendar obtained by extension earlier in time than its invention or implementation is called the "proleptic" version of the calendar, and thus we obtain the proleptic Gregorian Calendar. The Julian Calendar also can be extended backward as the proleptic Julian Calendar.

For example, even though the Gregorian Calendar was implemented on October 15, 1582 (Gregorian) we can still say that the date of the day one year before was October 15, 1581 (Gregorian), even though people alive on that day would have said that the date was October 5, 1581 (the Julian date at that time). Similarly, dates after October 15, 1582 (Gregorian) have equivalent, but different, dates in the Julian Calendar. For example, the first version of this article was completed on 1992-10-10 in the Gregorian Calendar, but it is also true to say that it was completed on 1992-09-27 in the Julian Calendar. As another example, the date of the winter solstice in the year 2012 is 2012-12-21 (Gregorian), which is 2012-12-08 (Julian).

Thus any day in the history of the Earth, either in the past or in the future, can be specified as a date in either of these two calendrical systems. The dates will generally be different; in fact they will be the same only for dates from March 1st, 200, to February 28, 300. The dates in neither calendar will coincide with the seasons in the distant past or distant future, but that does not affect the validity of these calendars as systems for uniquely identifying particular days. See also a note I sent to the CALNDR-L mailing list Re: Proleptic calendar conventions . 6. Variation in the Tropical Year The tropical year (a.k.a. the mean solar year) corresponds to the cycle of the seasons. The exact definition of this concept is currently a matter of debate among some astronomers (see Simon Cassidy's Error in Statement of Tropical Year ). All agree, however, that due to the gravitational dynamics of the Sun-Earth-Moon system the length of the tropical year (however defined) is changing slowly.

The length of the tropical year on 2000-01-01 is calculated by some astronomers to be 365.24218967 days, but at this level of precision the value depends on the definition of the concept.

The value changes significantly with the millennia, however, as follows (according to a formula in common use among astronomers): Year Length of tropical year in days -5000 365.24253 -4000 365.24250 -3000 365.24246 -2000 365.24242 -1000 365.24237 0 365.24231 1000 365.24225 2000 365.24219 3000 365.24213 4000 365.24207 5000 365.24201 Thus the value of the tropical year varies over this 10,000-year timespan by as much as .00052 days (about 45 seconds). 7.

Accuracy of the Gregorian and Orthodox Calendars As in any completely rule-based calendar, the Gregorian Calendar is not absolutely accurate. In the Gregorian Calendar the average length of a year is 365.2425 days (since there are 146,097 days in 400 calendar years). This is a lot closer to the "real" length of the solar year than is the case with the Julian Calendar. As noted above , the main competing values for the length of the solar year are 365.2422 days (the mean tropical year) and 365.2424 days (the vernal equinox year). The difference of the length of the Gregorian calendar year from the length of the real solar year is thus 0.0003 days (25.9 seconds) in the former case and 0.0001 days (8.6 seconds) in the latter case.

Were the length of the "mean solar year" to be constant this error would accumulate to one day after about 3,336 years (if we use the 365.2422 value) or after about 10,000 years (if we use the 365.2424 value). Whereas in the Gregorian Calendar a century year is a leap year only if division of the century number by 4 leaves a remainder of 0, in the Eastern Orthodox system a century year is a leap year only if division of the century number by 9 leaves a remainder of 2 or 6. This implies an average calendar year length in the Orthodox Calendar of 365.24222 days. This is very close to the present mean solar value of 365.24219, and the Eastern Orthodox Calendar is at present significantly more accurate in this respect than the Gregorian. Were the mean solar year to remain constant, the Orthodox Calendar would be off by one day only after about 33,000 years.

However over the next few millennia the Orthodox calendar, like the Gregorian, will become increasingly inaccurate with respect to the mean solar year until possibly recovering around 10,000 years from now. However, in terms of the vernal equinox year the Gregorian Calendar is more accurate than the Orthodox and will remain more accurate in the coming millennia. 8. True Length of the Tropical Year The tropical year has been defined as "the time it takes the Sun to appear to travel around the sky from a given point of the tropical zodiac back to that same point in the tropical zodiac." As Simon Cassidy has pointed out ( Error in Statement of Tropical Year ) this value depends on where in the Earth's orbit one begins the measurement of one revolution about the Sun. If the point used is the point of the vernal equinox then the value is 365.2424 tropical days (so this is the value of the "vernal-equinox year"). If one wishes an average value that is the mean of the values obtained by using different orbital starting points, then a value of 365.24219 days emerges.

Those interested in pursuing this question further should consult (in addition to the articles linked in the previous paragraph) the following: Royal Greenwich Observatory Give Us Our Eleven Days | The English calendar riots of 1752 Give us our eleven days Navigation By Ben Johnson | Comments ‘Give us our eleven days!’ The English calendar riots of 1752. The eleven days referred to here are the ‘lost’ 11 days of September 1752, skipped when Britain changed over from the Julian calendar to the Gregorian calendar, bringing us into line with most of Europe. The Gregorian calendar is today's international calendar, named after the man who first introduced it in February 1582, Pope Gregory XIII. Before 1752, Britain and her Empire followed the Julian calendar, first implemented by Julius Caesar in 46 B.C. However this calendar had an inbuilt error of 1 day every 128 years, due to a miscalculation of the solar year by 11 minutes. This affected the date of Easter, traditionally observed on March 21, as it began to move further away from the spring equinox with each passing year.

To get over this problem, the Gregorian calendar was introduced. This is a solar calendar, based on a 365-day year divided into 12 months. Each month consists of either 30 or 31 days with one month, February, consisting of 28 days. A leap year every 4 years adds an extra day to February making it 29 days long. First to adopt the new calendar in 1582 were France, Italy, Poland, Portugal and Spain. Turkey was the last country to officially switch to the new system on January 1st, 1927. The Calendar (New Style) Act 1750 introduced the Gregorian calendar to the British Empire, bringing Britain into line with most of Western Europe. Its introduction was not straightforward. It meant that the year 1751 was a short year, lasting just 282 days from 25th March (New Year in the Julian calendar) to 31st December. The year 1752 then began on 1 January. There remained the problem of aligning the calendar in use in England with that in use in Europe.

It was necessary to correct it by 11 days: the ‘lost days’. It was decided that Wednesday 2nd September 1752 would be followed by Thursday 14th September 1752. Claims of civil unrest and rioters demanding "Give us our eleven days" may have arisen through a misinterpretation of a contemporary painting by William Hogarth. His 1755 painting entitled: "An Election Entertainment” refers to the elections of 1754 and depicts a tavern dinner organised by Whig candidates. A stolen Tory campaign banner with the slogan, "Give us our Eleven Days" can be seen lower right (on the black banner on the floor under the seated gentleman’s foot). The Tories can be seen outside the window, demonstrating. The changing of the calendar was indeed one of the issues debated in the election campaign of 1754 between the Whigs and the Tories. It is also true that when the British government decided to alter the calendar and skip these 11 days, many people mistakenly believed that their lives would be shortened by 11 days. People were also unhappy and suspicious at the moving of saint's days and holy days, including the date of Easter.

Many people also objected to the imposition of what they saw as a 'popish' calendar. However, most historians now believe that these protests never happened. You could say that the calendar rioters were the late Georgian equivalent of an urban myth. Not everyone was unhappy about the new calendar. According to W.M. Jamieson in his book, 'Murders Myths and Monuments of North Staffordshire', there is a tale about one William Willett of Endon. Always keen on a joke, he apparently wagered that he could dance non-stop for 12 days and 12 nights. On the evening of September 2nd 1752, he started to jig around the village and continued all through the night. The next morning, September 14th by the new calendar, he stopped dancing and claimed his bets! Footnote: Have you have ever wondered why the tax year in Britain starts on the unlikely date of 6th April, rather than 1st January? The official start of the year on the Julian calendar used to be Lady Day (25th March), and this was also the official start of the tax year.

However the introduction of the new calendar and the loss of the eleven days in 1752 meant this date was changed to 5th April in 1753, to avoid losing 11 days of tax revenue. Another change was made to the date in 1800, as this would have been a leap year in the Julian calendar but not in the new Gregorian calendar. So again the tax year was extended and the date changed to 6th April where it remains to this day. Tweet If you enjoyed this article, you might also like... Leap Year Superstitions - The 29th February is an especially important day. Anything started on this day is said to be assured of success! Harris's List - Harris's List of Covent Garden Ladies was an annual directory of prostitutes working in London published from 1757 to 1795, and was a Georgian bestseller. The Hanging of the Hartlepool Monkey - Legend has it that during the Napoleonic Wars of the early 19th century, a shipwrecked monkey was hanged by the people of Hartlepool, believing him to be a French spy!

To this day, people from Hartlepool are affectionately known as... William Hogarth and 18th century life - In the early 18th century, Georgian Britain was a nation openly and often shockingly rude, especially to 21st century eyes. A gifted commentator on his times, Hogarth’s shockingly satirical and sometimes brutal works transport us back to... Popular This Month The Gregorian Calendar—History Religious and Secular Holidays 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 days—that 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 11½ 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 seconds—accurate 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 29½ days long) is only 354 days, 8 hours long; a solar year lasts about 365¼ 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 365¼-day year doesn't exactly lend itself to equal subdivision (the 71¼-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 intercalation—the 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 Passover —and 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, 1792—the 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. Did you know?

Question: How many days did Britain "lose" in September 1752 on changing from the Julian to the Gregorian calendar?
Answer: 11