Family History Database Calendar Considerations by Vic Berecz – August 2003 – Updated September 2018 Purpose and Overview The purpose of this short paper is to rationalize the positions we have taken regarding dates provided in the Berecz-Luhrs Master Database of family history. It is generally our assumption that dates given in the database are from the Gregorian calendar and that the each year begins on January 1st. This is because virtually all dates in this database were recorded in places/times when the Gregorian calendar was in use with January 1st as the beginning of the year. Two potential problems with this approach have surfaced to date. The German Problem creates a somewhat significant issue, but the Hungarian Problem becomes essentially a non-issue. These problems are discussed below, and our approach to them is documented. Other problems may surface in the future (for example if we are able to trace Irish ancestral lines back to before 1752), but we will deal with these if and when we encounter them. The Julian calendar was created by Julius Caesar in 45 BC and has a leap year every four years. Over the centuries a small error accumulated, until by the 1500s an error of 10 days started to have an effect on everyday life. Such important decisions, as when to plant crops, were being impeded. As a result, a revision to the calendar was necessary. The Gregorian calendar is the calendar in common civil use today throughout the world. It was proposed by Aloysius Lilius, a physician from Naples, and was mandated by the Council of Trent (1545- 1563) to correct the errors of the Julian calendar. Pope Gregory XIII promulgated the papal bull Inter Gravissimas on 24 February 1582 making the Gregorian calendar the official calendar of the Roman Catholic Church. Beginning the year on January 1st has been the accepted practice in most countries since at least 1600. Great Britain and its dominions (including the U.S. and Ireland) used March 25th as the first day of the year until 1752, when they adopted the Gregorian calendar as well as a January 1st New Year. The normal approach to this is to designate January 1st to March 25th dates before this change by “OS” which stands for “Old Style.” We have not encountered this problem yet in our database. Adoption of the Gregorian Calendar by Countries of Interest Adoption of the Gregorian calendar involved skipping 10 or more days (depending upon the precise time the change was made). This was accomplished by simply decreeing that a given day – say October 21 – was followed by a normally non-contiguous day – say November 1 as was the case in Hungary in 1587. Roman Catholic countries adopted the Gregorian calendar early, meaning that Hungarian and Spanish dates are not an issue for us since all extant records use Gregorian dates. [Note: both these countries were under the control of the Roman Catholic Habsburg family.] Some countries did not adopt the Gregorian calendar until relatively recently; fortunately, we don’t have to deal with any of those. Listed here are the countries in which the great bulk of people in our database resided. Note that what is now the U.S. and Ireland adopted the Gregorian calendar with Great Britain – to which they were a dependency at the time in question. Spain: 4 Oct 1582 was followed by 15 Oct 1582 Hungary: 21 Oct 1587 was followed by 1 Nov 1587 Germany: Different states adopted on different dates, with many local variations: Roman Catholic states: on various dates in 1583-1585. Prussia: 22 Aug 1610 was followed by 2 Sep 1610. Other Protestant states: 18 Feb 1700 was followed by 1 Mar 1700. Great Britain and Dominions: 2 Sep 1752 was followed by 14 Sep 1752. Sweden: Sweden is a real anomaly in the calendar conversion process. 1 Family History Database Calendar Considerations They 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.) That was the plan. So 1700 (which should have been a leap year in the Julian calendar) was not a leap year in Sweden. However, for political reasons the Swedish Parliament chose to make 1704 and 1708 leap years. Sweden was therefore out of synchronization with both the Julian and the Gregorian worlds. As a result, 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, as was done in Great Britain the previous year. You ask, Why is Sweden a country of interest to us? The Swedish king ruled several parts of northern Germany in accordance with the terms of the Peace of Westphalia that ended the 30 Years War in 1648. The areas in northwestern Germany ruled by Sweden were the Duchy of Bremen and Verden and a few adjacent parts of the County of Hoya. These are the areas where most of Joan’s ancestors lived. The Great Nordic War was fought from 1700-1721 with Denmark, Poland, Russia allied to suppress Sweden’s dominant position in northern and eastern Europe. In 1705, the Duchies of Calenberg and Lüneberg combined to form the Electorate of Hannover. The rulers of German states who were designated Electors of the Holy Roman Empire were a very powerful and important group. In 1714, the Elector of Hannover also became king of Sweden’s ally, Great Britain. He is known to us as King George I. A treaty between Sweden and Hannover that was ratified on November 1, 1719 made Sweden’s northwest German territories a part of Hannover, presumably in exchange for Britain’s help in bringing the Great Nordic War to an end. For more on why all this matters to our family history see the German Problem below. Calculation of Day of the Week The following algorithm will compute the day of the week for the Julian or Gregorian calendars. All divisions are integer divisions in which the remainders are discarded. Note that there are only 14 possible calendars for any given year. So, we can use recent calendars to view historical calendars. Calculation of the Date of Easter Easter and other dates based upon it have been a problem throughout the history of Christianity – the 11th century schism between Roman Catholicism and Eastern Orthodoxy was, to an extent, based on differences relating to the date of Easter. This calculation is derived from an old Hebrew lunar calendar and so the dates of Easter do not repeat regularly. Easter Sunday is the first Sunday after the first full moon after the vernal equinox. For this calculation, the vernal equinox is considered to be March 21. But, in fact, the astronomical vernal equinox may vary by 1 or 2 days from March 21. A simplified algorithm for computing the date of Easter is provided below, but it is not very simple. Again, all 2 Family History Database Calendar Considerations divisions are integer divisions, with remainders discarded. Note that in this algorithm, “I” is the number of days from March 21 to the Paschal full moon. The biggest problems with the calculation of the date of Easter, as noted above, involve not the algorithm, but the differences between the western churches and the eastern (Orthodox) churches. This, fortunately, it is not an issue for this database, since no eastern Orthodox records have been used here so far. But, there is one minor glitch that does affect us. Historically, some countries have used the real (astronomical) vernal equinox instead of the official one (March 21) when calculating Easter. This was the case in the German Protestant states (including Hannover), which used the astronomical data to establish the date of Easter in the years 1700-1776. Therefore, German dates computed relative to the date of Easter in the early 1700’s are always suspect. Several such dates exist in our database – see the German Problem below. The German Problem Most of Joan’s ancestors came from a part of Germany that was controlled by Sweden until 1719. After that date, the residents of this region found themselves in Hannover until its incorporation into the Prussian-led German Reich in the 1860s. To date, we have found only a small number of recorded German dates that precede 1700. These are mostly from the church records of Wilstedt and Daverden that were recorded in the normal day-month-year manner. An example is the baptism of Peter Schnakenberg of Vorwerk on 02 Feb 1693 – he is one of Jake’s 7th-great-grandfathers. Though these dates obviously use the Julian calendar, they present no problem in this database and are recorded as found in the records. 3 Family History Database Calendar Considerations Note: during the Napoleanic Wars, France occupied Hannover for a few years. I am told that some German records exist using the French Republican Calendar. But, so far I have not found such records for our family. But, recently we found ancestors of our daughter-in-law who lived in France and the French colony of Sainte-Dominique, now Haiti. So, it also became necessary to address this issue … see French Republican Calendar below. Likewise, for the period 1700-1719 any of the German dates that we find recorded may be using the Gregorian calendar, or the Swedish calendar – which was one-day off from the Julian calendar from March 1, 1700 until February 30, 1712 – and corresponded with the Julian calendar from then until after the Swedish presence in Germany had ended.