The modern calendar of Europe is the Gregorian calendar which was implemented in 1582 by Pope Gregory XIII. It replaced the Julian calendar, which had been in use since the fourth century. The conversion of dates kept in the earlier Julian form requires both precision in the historical identification of the problem and proper calculations.
If everyone in Europe had converted from the Julian calendar to the Gregorian calendar at the same time, this program would not be necessary. Unfortunately, different regions of Europe adopted the Gregorian calendar at different times ranging from the initial adoption by the Roman Catholic Church in 1582 through the early twentieth century in countries such as Russia, Greece and Turkey.
The problem which both the Gregorian and Julian calendars try to fix is that the solar year is not exactly 365 days long. Both calendars try to keep the same annual solar events on the same days of the calendar year. The Julian calendar makes the assumption that the year is 365.25 days long, while the Gregorian calendar assumes that the year is 365.2425 days long.
The spring equinox was set to the date 21 March in the year 325 by the council of Nicea. By the year 1582, the spring equinox was occurring on the 11th of March. As a result of generations of concern, the pope ordered that 10 days would be removed from the calendar so that the spring equinox would return to 21 March. It was decided that the days 5-14 October from the year 1582 would be skipped during the transformation from the Julian to Gregorian calendar. (Those dates were acceptable because there were no important feasts taking place during the days being skipped).
There was great resistance to the adoption of the Gregorian calendar, and its acceptance was determined locally. Protestant and Orthodox parts of Europe were particularly resistant. In general the Protestant world adopted the Gregorian calendar in the eighteenth century, while the Orthodox world did not accept it until the twentieth. For example, England converted in 1752, while Russia and Greece did not adopt the Gregorian calendar until 1918 and 1924 respectively.
The year of pagan Romans at the start of the fourth century had begun on January first. Christian communities were encouraged to differentiate themselves by adopting more significant feast days for the start of the year. The first day of the year in the Julian calendar was March 25. Ironically, the Gregorian reform re-instituted January 1 as the first day of the year.
The hcal program does not currently make provisions for variation in year demarkations, but some of the principal traditions are noted in section 4 below
Some regions adopted the first of January as the beginning of the year before they adopted the Gregorian calendar. Other regions, such as Venice, kept March 1 as their new year even after they adopted the Gregorian calendar -- until the collapse of the Republic of Venice in 1797.
There was great fragmentation of time-keeping methods in some parts of Europe over the first two or so centuries of Gregorian reform. Almost every province of Germany and Switzerland, for example, had an independent practice, often reflecting vicissitudes in its religious persuasion. Sweden reverted to the Julian calendar in 1600 after once switching to the Gregorian calendar and did not re-adopt the Gregorian calendar again until 1753.
The hcal program takes as input one of the following locales to generate a historic calendar for the specified region.
|Austria||calendar for Austria [also Bohemia and Slovakia] created by dropping the days 7-16 January from the year 1584.|
|Bavaria||calendar for Bavaria and other South German provinces created by dropping the days 6-15 October from the year 1583.|
|England||calendar for the United Kingdom (England, Scotland, Wales, Ireland, and the British colonies created by dropping the days 3-13 September 1752.|
|France||calendar for France created by subtracting the days 10-19 December from the month of December 1582. (The French Revolutionary calendar is not considered in hcal).|
|Greece||calendar for Greece created by dropping the days 10-22 March 1924.|
|Gregorian||generates a Gregorian calendar for all input dates|
|Holland||calendar for Amsterdam, Delft, Haarlem and Rotterdam created by dropping the days 22-31 December from the year 1582.|
|Hungary||calendar for Hungary [also parts of Poland] created by dropping the days 22-31 October from the year 1587.|
|Italy||calendar for Rome (Italy) [also Portugal, Spain, and parts of Poland] created by subtracting the days 5-14 October from the year 1582.|
|Julian||generates a Julian calendar for all input dates|
|Norway||calendar for Norway [also Denmark and many North German provinces] created by dropping the days 19-28 February from the year 1700.|
|Russia||calendar for Russia and the other provinces of the former U.S.S.R. created by dropping the days 1-13 February from the year 1918.|
|Switzerland, Lucerne||calendar for Lucerne, Uri, Zug and Friburg created by dropping the days 12-21 January from the year 1584.|
|Switzerland, Zurich||calendar for Zurich, Bern, Basil, Geneva, and Baden created by dropping the days 1-11 January from the year 1701.|
|Turkey||calendar for Turkey created by dropping the days 19-31 December from the year 1926.|
The Julian calendar is usually 365 days long. If the year is divisible by 4 without a remainder, then the 29th of February is added to the year making the length of the year 366 days.
1 Jan of the year 1 A.D. is on Saturday in the Julian calendar and is on Monday in the Gregorian calendar (the Gregorian calendar is two days behind the Julian calendar at this point).
The Gregorian calendar is similar to the Julian calendar, but if the year is divisible by 100, then there is no leap day in that year; however if the year is divisible by 400, then the leap day is included. Thus, the year 2000 is a leap year in the Gregorian calendar, but the year 1900 is not.
The first day for which the two calendars are in synchronization is 1 March 200. From then through 28 February 300, the dates in each calendar are identical, e.g., the date 5 May 267 in one calendar is also the date 5 May 267 in the other calendar.
The day of the week is always the same for days occurring in the Julian and Gregorian calendars (e.g., Tuesday in the Gregorian calendar is always Tuesday in the Julian calendar) ; however, the day of the month for any given solar day is different in each calendar. About once a century, the Julian calendar shifts ahead of the Gregorian calendar by one day. The table below shows the number of days by which the Julian calendar is in advance of the Gregorian calendar:
No. of days Julian dates are Years ahead of Gregorian dates. ================================================== 201 - 299 0 301 - 499 1 501 - 599 2 601 - 699 3 701 - 899 4 901 - 999 5 1001 - 1099 6 1101 - 1299 7 1301 - 1399 8 1401 - 1499 9 1501 - 1699 10 1701 - 1799 11 1801 - 1899 12 1901 - 2099 13 2101 - 2199 14
Note that Gregorian calendar dates before October of 1582 are only meaningful in a retroactive sense and were not known or utilized by earlier periods of history. Gregorian dates earlier than October of 1582 are therefore termed proleptic (i.e., hypothetical).
New Year = March 1:
New Year = March 25 (Feast of the Annunciation):
New Year = Easter (movable):
New Year = September 1:
New Year = December 25 (Christmas):
The following references are particularly recommended. Starred items were consulted in determining the dates on which the Gregorian calendar was adopted.