History of the Calendar
The Need for a Calendar
The Seven Day Week
The fixed 7-day week is so much a part of daily life that it is commonly assumed to be as old as human society. It is not known for sure when the system of fixed 7-day weeks, with no relation to the lunar cycle, came into use, but probably lie in Sumerian/Babylonian culture. Some Historians believe that around 2350BC. Sargon I, King of Akkad, having conquered Ur and the other cities of Sumeria, instituted a seven-day week, the first to be recorded. The Jews were commanded to observe "the seventh day" as one on which no work was to be performed (in contrast to the other days when work was done). If this is understood as every seventh day (rather than the seventh day of some period such as the month) then a sequence of fixed 7-day weeks emerges. The fixed 7-day week was not widely used until it was introduced into the Julian Calendar in the 4th Century CE by the Emperor Constantine. Through accidents of history, the Gregorian Calendar has come to be used worldwide as the standard civil calendar for government and business affairs. No improvement has been made in this calendar since it was decreed by Pope Gregory in 1582.
Although some forms of life exhibit cycles of 29-30 days (influenced by the Moon) there is no naturally occurring cycle of seven days. In human society at present this cycle runs on continuously but it has no harmonious relation with the other units of time, the month and the year. The 7-day week exists solely because of social habit and religious tradition, with otherwise no justification. The synodic month (a.k.a. the mean lunar month) is the mean (that is, average) interval in days between exact conjunctions of the Moon and the Sun (as observed from the Earth). The current value of the synodic month (rounded to six decimal places) is 29.530588 days.
The story of Noah contains many allusions to seven days. Note the following in Chapters 7 and 8 of Genesis:
Do Weeks of Different Lengths Exist?
If you define a "week" as a 7-day period, obviously the answer is no. But
if you define a "week" as a named interval that is greater than a day and
smaller than a month, the answer is yes
In international standard ISO-8601 the International Organization for Standardization (ISO) has decreed that Monday shall be the first day of the week.
The Lunar Year
|Most calendars are based on the solar year. Solar years have
the disadvantage of not being easily observable. Many years of observations
are required to fix them with any significant degree of accuracy. On the
other hand, the phases of the Moon -- and the first visibility after the new
moon in particular -- are very easy and quick to observe. Therefore, the
first calendars defined a lunar year, usually consisting of 12 synodic
months. A synodic month is the interval from one new moon to the next and
lasts 29.530588 days. This is equivalent to 29 days, 12 hours, 44 minutes
and 2.9 seconds. Since for practical reasons a month should contain an
integer number of days, most calendars alternated between months of 29 and
30 days, respectively. A year made out of six months of each type has 354
days and is thus too short by 0.3672 days as compared with a true lunar
year. Therefore lunar calendars have to insert one leap day about every
third year to keep in step with the moon phases. A pure lunar calendar is
not synchronous with the seasons and after 16 years will put the winter in
the summer and vice versa. Over a period of 32 years it will cycle through a
The Luni-Solar Year
A luni-solar year is the attempt to combine the phases of the moon and the seasons into one calendar. This is possible if leap months are inserted. Several schemes were used in history. The best known solution was found by the Greek Meton in the year 432 BC but apparently was known to other cultures before. The Metonic cycle encompasses a total of 235 months of which 125 are full (i.e. they have 30 days) and 110 are `hollow' (having 29 days). The months are combined into 12 normal years with 12 months each and 7 leap years with 13 months each. The cycle covers 6940 days whereas 225 synodic months sum up to 6939.688 days and 19 tropical years to 6939.602 days. The difference in motion between Sun and Moon amounts to only 0.0866 days so that eclipses repeat in the Metonic cycle with high accuracy. No correction applied
The Hebrew Calendar
The year is divided into 12 lunar months which each start when the new moon is first visible. This gives a total of approx 354 days. The result of this is that the entire year moves 11 or 12 days per year. This was compensated for by adding an additional month seven times in every 19 years.
The names of the Jewish months are - Tishrei (formally Abib), Iyyar (formally Ziv), Sivan, Tammuz, Av, Elul, Tishri (formally Ethanim), Marchesvan (Bul), Kislev, Tebet, Shebat and Adar. In a leap year Adar I is followed by Adar II. The months of Marchesvan and Kislev vary in length to make the year length correct. The new year starts on the first day of the first new moon after the vernal equinox. However there are some days of the week on which the year cannot start as certain holidays cannot precede or succeed the Sabbath. This means that some years a day is added, or removed, to ensure that the day/date rules are abided by.
An ordinary year consists of 353, 354 or 355 days. A leap year consists of 383, 384 or 385 days. These three lengths of each type of year are known as 'deficient', 'regular' and 'complete' years.
To make the weeks work out, eleven days were subtracted and three real days were eliminated to make this adjustment, which puts our calendar out of sync with time measured prior to this change. Count the days.
link article: How Britain got the Calendar Wrong Greece: 9 Mar 1924 was followed by 23 Mar 1924 Hungary: 21 Oct 1587 was followed by 1 Nov 1587 Italy: 4 Oct 1582 was followed by 15 Oct 1582 Japan: Different authorities say: 19 Dec 1872 was followed by 1 Jan 1873 18 Dec 1918 was followed by 1 Jan 1919 Latvia: During German occupation 1915 to 1918 Lithuania: 1915 Luxembourg: 14 Dec 1582 was followed by 25 Dec 1582 Netherlands: Brabant, Flanders, Holland, Artois, Hennegau: 14 Dec 1582 was followed by 25 Dec 1582 Geldern, Friesland, Zeuthen, Groningen, Overysel: 30 Nov 1700 was followed by 12 Dec 1700 Norway: Then part of Denmark. Poland: 4 Oct 1582 was followed by 15 Oct 1582 Portugal: 4 Oct 1582 was followed by 15 Oct 1582 Prussia : 22 Aug 1610 was followed by 2 Sept 1610 Romania: 31 Mar 1919 was followed by 14 Apr 1919 Russia: 31 Jan 1918 was followed by 14 Feb 1918 Spain: 4 Oct 1582 was followed by 15 Oct 1582 Sweden (including Finland): 17 Feb 1753 was followed by 1 Mar 1753 (see note below) Switzerland: Catholic cantons: 1583 or 1584 Zurich, Bern, Basel, Schafhausen, Neuchatel, Geneva: 31 Dec 1700 was followed by 12 Jan 1701 St Gallen: 1724 Transylvania : 14 Dec 1590 was followed by 25 Dec 1590 Turkey: 18 Dec 1926 was followed by 1 Jan 1927 Tyrol : 5 Oct 1583 was followed by 16 Oct 1583 USA: See Great Britain, of which it was then a colony. Yugoslavia: 14 January 1919 was followed by 28 January 1919 but parts of the country had changed over earlier.
Sweden has a curious history. Sweden decided to make a gradual change from the Julian to the Gregorian calendar. By dropping every leap year from 1700 through 1740 the eleven superfluous days would be omitted and from 1 Mar 1740 they would be in sync with the Gregorian calendar. (But in the meantime they would be in sync with nobody!)
So 1700 (which should have been a leap year in the Julian calendar) was not a leap year in Sweden. However, by mistake 1704 and 1708 became leap years. This left Sweden out of synchronisation with both the Julian and the Gregorian world, so they decided to go ‘back’ to the Julian calendar. In order to do this, they inserted an extra day in 1712, making that year a double leap year! So in 1712, February had 30 days in Sweden.
Later, in 1753, Sweden changed to the Gregorian calendar by dropping 11 days like everyone else.
It should be noted that the Gregorian Calendar is useless for astronomy because it has a ten-day hiatus in it. For the purpose of calculating positions backward in time, astronomers use the Julian Date Calendar.
Calendar changes over time...
The Julian calendar, introduced by Julius Caesar in 45 BC, began on 1st January, with the length of months alternating between 31 and 30 days - except for February, which had 30 days in a leap year and 29 days otherwise. (This replaced an earlier Roman calendar which had 10 months of alternating 30 and 31 days, followed by a "winter gap", the length of which varied from year to year. The last year of this old calendar actually had 445 days.)
Complications to the Julian system began when the Senate wanted to name a month after the then Emperor Augustus. To avoid slighting the Emperor, the month named for Augustus must be as long as the month named for Julius, and should follow it directly. And so July and August became 31 days each, and February surrendered an extra day. (To avoid 3 successive 31 day months, September was shortened to 30 days, October lengthened to 31, and so on.)
The Romans initially introduced leap years every 3 years, but by about 9 BC it was seen that the calendar was getting out of step with the solstices, so leap years were abandoned altogether, until about AD 4 or 8, when leap years were re-introduced as every 4 years. Even this was not completely accurate, giving an error of 45 minutes in 4 years, or 3 days in 400 years. In time, this miscalculation became quite noticeable.
Around 150 AD Christian churches decided to take over the pagan festival of Saturnalia (the winter solstice) and celebrate 25th December as Christ's birthday. Later, when the cult of the Virgin Mary became popular, it was thought that the Christian era should start on the day of Christ's conception, that is, 9 months earlier on 25th March, which they named Ladyday. The year began on 25th March and ended on the following 24th March.
All moveable feasts in the church calendar relate to Easter. In turn, gospel tradition related Easter to the Jewish festival of Passover, which in turn was related to the spring equinox, the phase of the moon and the celebration of the Sabbath. Over the centuries, by following the Julian calendar, the Easter festival was slowly but surely moving away from the spring equinox towards the summer solstice. The new system adopted by Pope Gregory in the 16th century, specified a calendar with a year length of 365 days, 5 hours, 40 minutes, 20 seconds. Therefore 3 days had to be dropped every 400 years. So those years which were divisible by 100 would only be leap years if they were divisible by 400. To correct errors which had built up over centuries, Pope Gregory declared that Thursday 4th October 1582 in the Julian Calendar should be immediately followed by Friday 15th October in the Gregorian Calendar.
Scotland and most Roman Catholic countries of Europe adopted the Gregorian Calendar in 1582 or soon after. Most Protestant countries however ignored this Papal decision for another 200 years. In England, they still followed the old Julian Calendar (year ending 24th March) until 1751. Lord Chesterfield's Act of 1751/2 stated that the year 1752 would begin on 1st January and end on the following 31 December. In addition, in 1752 only, the calendar was adjusted to omit 11 days (2nd September was followed by 14th September) to bring their "new" (Gregorian) calendar back in line with most of the rest of Europe.
Orthodox countries (those following allegiance to the Patriarch of Constantinople) were even slower to change. Russia, for example, did not convert to the new calendar until after the Russian Revolution. An interesting consequence of this was that when London hosted the 1908 Olympic Games, the Russian team arrived 12 days late because of it! Turkey was the last major European country to adopt the Gregorian Calendar - on 1st January 1927.
In England, the "quarter days" (for quarterly events like the Quarter Court sessions) were Lady Day (March 25) when the legal year started, St John the Baptist Day (Midsummer Day, June 24), Michaelmas (September 29) and Christmas (December 25). These were close to the equinoxes and solstices and were regarded as the beginning of the dates of the seasons. In the City of London, when the calendar changed, bankers refused to pay their taxes 11 days early, and so would not pay before 5th April, which still remains the date of the end of the fiscal year.
When reading English dates prior to 1752, regard the years with care. Was the date written by someone from that time? - in which case remember the year ran from March to March. However if the date was written by a modern researcher, did they understand the calendar in place at the time - and what system were they using when they described a date such as 2nd January 1701? To avoid confusion the convention is to write that date as 2nd January 1701/2 which uniquely identifies the year. (1701 in this case being the year according to the old Julian Calendar, and 1702 according to the "new" Gregorian Calendar.)
an article by Kerry Farmer