The Julian Calendar

The astronomer Sosigenes from Alexandria was given, by Julius Caesar, the task of designing an easy-to-use and exact calendar. Sosigenes assumed that the year had a length of 3651/4 days and worked out the leap year rule, by which three common years should be followed by one leap year, the former having 365 days each, while the latter should have 366 days. The months were no longer to be determined by the moon's phases and were given lengths of 30 or 31 days. The length of February was not changed in common years, while in leap years the extra day was to be inserted after 24 February. To align the calendar with the sun, two extra months were inserted, giving this year 445 days, which is why it was called the "annus confusionis". For more on the Roman counting of days see The Roman Calendar.

Even the relatively simple leap year rule was, it seems, too complicated for many Romans. Instead of making ever fourth year a leap year, this was done with every third year, which made another reform necessary. This was carried out under Caesars successor Augustus by making three leap years common years until the calendar was aligned with the sun again.

The years were counted "after the foundation of the city" (ab urbe condita), which was thought to have happened in 753 BCE. After August's reform, the Roman year 761 and every fourth year became leap years. Only by coincidence this year corresponds to our year 8, which is divisible by 4.

The counting of the years according to our common era was suggested by the monk Dionysius Exiguus in the 6th century, but only from the 9th century this era became the ordinary counting in Europe.

The monk Dionysius Exiguus had to establish new Easter tables in 525 since the tables then used were to expire in 531. In his new tables Dionysius used years "from the Incarnation of our Lord Jesus Christ" rather than the Diocletian era that was in use then. Dionysius may have disliked an era being used in Christian chronology commemorating an emperor who was responsible for the last large-scale repressions against Christians. Dionysius did not tell how he derived the date of the Incarnation in year 1 CE. Since Easter dates of the Julian calendar repeat after 532 years (see Calculation of Easter), the reason for establishing an era in such a way that the Easter tables start in 532 may have been practical considerations. Another convenient feature is that leap years get numbers that are divisible by four. Dating according to this era did not become common until the 9th century. Until then, and even later, World eras or the Diocletian era were used.

The Julian calendar was used until as late as the beginning 20th century, some Orthodox Churches still using it for determining some of their feast days. In the Middle Ages already, the days in the months were simply counted instead of hanging on to the rather intricate Roman system.

Sosigenes' leap year rule made four years have 1461 days, resulting in an average length of one year of 365.25 days, which is about 11 minutes longer than the exact length of the year. This difference had amounted to 10 days in the 16th century, which meant that the beginning of the year (1 January) had slowly moved towards spring.

Today, the difference between the Julian and the Gregorian calendar is 13 days. With some Orthodox churches celebrating several feast days according to the Julian calendar, their Christmas Day falls on 7 January of the following year, according to the Gregorian calendar.

Beginnings of the Year

Our New Year's Day, 1 January, was introduced by the Romans, which earlier started their year with 1 March. In the Middle Ages some different days came into use as the Beginning of a year because of some pre-Christian New Year's rituals not liked by the emerging Christian church.

Circumcision Style

This is the beginning of the year with 1 January, on which, in the 7th century, the circumcision of Christ, was put, because it was hard to overcome that day as the start of a new year. In civil life, the new year was merely always celebrated on this day, despite different styles in use officially. For official dating, this style was commonly used only since the introduction of the Gregorian calendar. The Papal office has been using this style for brevets since 1621, for bulls since 1691. Other styles have been replaced by 1 January for instance in France in 1563, in the Netherlands and in the diocese Geneva in 1575, in Florence and Pisa in 1749, in England together with the introduction of the Gregorian calendar in whole Britain in 1753, and finally in the diocese Treves during the 30-years-war (1618-1648).

Christmas Style

The birth of Christ being celebrated on Christmas day, 25 December, the beginning of the new year was put on this day. In this style 24 December 851 was followed by 25 December 852. This style was used widely in Germany. Documents of the royal or imperial office were dated according to this style without exception until the beginning 13th century. During the reigns of the kings from Philipp (r. 1198-1208) to Konrad IV. (1237/50-1254), the Annunciation style was used sometimes, but since Rudolf I. (r. 1273-1291) Christmas and Circumcision styles were both used.

Other territories in which the Christmas style was in use were the territories of the Order of the Teutonic Knights, the spanish Netherlands (large parts of what is now Belgium), where the Circumcision style was officially introduced in 1575, and England, where the Christmas style was replaced by the Annuctiation style during the 13th century. In Spain, the Annuntiation style was abolished and the Christmas style adopted in 1350 (Aragon) and 1383 (Castilla) until 1556, when the Circumcision style was introduced.

In the German dioceses the Christmas style was used, with some exceptions (e. g. Treves, Münster).

Annunciation Style

This use makes the year begin on 25 March, the day of the annunciation of the Incarnation. The Incarnation having to have taken place before the birth of Christ, the year should have started on 25 March of the preceding year by means of our "normal" calculation. Thus, year 1405 of the Incarnation must begin on 25 March 1404 and end on 24 March 1405, Julian. But, only in Pisa and the territories influenced by this city this calculation, the calculus pisanus, was adopted. In Florence the year 1405 of the Incarnation started on 25 March 1405 and ended on 24 March 1406, Julian. This was called the calculus florentinus. A great disadvantage of this style is the possibility of Easter occurring not at all, once, or twice in a year.

In Germany, the diocese of Treves used the Annunciation style until the 30-year-war (1618-1648), in Luxemburg and Lotharingia it was used until 1575 and 1579, respectively.

In Britain, the calculus florentinus was in use until the year 1751, which began on 25 March 1751, Julian. The succeeding year 1752 was decreed to begin on 1 January 1752, Julian, and in September that same year, the Gregorian calendar was adopted. Thus, the year 1751 had a length of only 282 days, and 1752 was shortened again, by 11 days, 2 September being followed by 14 September.

The Papal office dated documents according to the Annunciation style from the 10th century until the 13th century, using the calculus Florentinus. Under the popes from Urban II. to Lucius II., the calculus Pisanus was observed sometimes. In France, the Annunciation style could be found from the end of the 10th century until the 12th century, when the Easter style followed. Finally, the Swiss diocese Lausanne used the Annuntiation style until the 16th century.

Easter Style

This style lets the year begin on Easter saturday, but there were different uses, which made the year begin on Good Friday already (e. g. in Flanders and Brabant). The feast of Easter falls on a day somewhere between 22 March and 25 April, and this led to the possibility of a date occuring twice a year. The two dates had to be distinguished by marking them "after Easter" and "before Easter".

The Easter style was mainly used in France since the reign of king Philipp I (r. 1059/60-1108). Only as late as 1563 the Circumcision style was adopted officially. In Germany, documents of the diocese of Cologne were dated in the Easter style, which was then replaced by the Christmas style in 1310. In Flanders, Brabant, and Hennegau, which are all parts of the Netherlands, and in the Swiss dioceses of Geneva (from around 1220 until 1305) and Sitten (from around 1200 until around 1250), the Easter style was observed, too. In the Swiss dioceses mentioned, the Christmas style was adopted then.

1 March

The original Roman beginning of the year on 1 March was in use in the Republic of Venice until 1797, when the republic broke down. In Russia, the year began on 1 March until the 14th century, when the beginning of the year was moved to 1 September.

The original Roman Beginning of the year on 1 March was in use in Russia until the 14th century. In the Republic of Venice this was the official style until it was swept away by the French in 1797.

1 September

Since the 13th century, this style became common in Russia, where it was used until the adoption of the Julian calendar. The years were counted "after the creation of the world", so 31 August 1522 Julian was designated 31 August 7030 in Russia. The succeeding day was 1 September 7031.


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