Understanding Genealogical Dates
If you are comparing two records and can't understand
why the date of birth (for example) is slightly different when all the
other information indicates it is the same person, the reason may be
that the different records used Julian and Gregorian dates.
For example : 27 April 1332 (Julian calendar) is 5 May 1332 (Gregorian
calendar).
Note also that the conversion has a margin of error of one day 50% of the time (e.g. half of the date conversions will be out by one day). So the date above could be 4 May or 6 May.
Date Converter (created by Ian MacInnes, Albion College)
You can compare dates by going to the following page -> Link here
Note that he refers to New style and Old style dates, with Gregorian being the New style
The following comment is courtesy of N. B. Macdonald
The historical calendar changes are fascinating. A couple of countries to watch out for are Scotland and Sweden. It is easy to assume that Scotland did as England did, but Scotland switched to New Years Day = first of January 152 years before England, in 1600, while they did change from the Julian to the Gregorian calendar at the same time as England did. Sweden wavered and twice did not implement changes as decided. Once they changed their minds and once they apparently forgot. In 1712 Sweden had 2 leap days.
The British parliament eliminated the dates 03-13 Sep 1752. In Denmark/Norway: 18 Feb 1700 was followed by 01 Mar 1700.
One has to remember that sections of North America were using different systems at the same time. Some followed Great Britain, some France and some Spain. Part of Nova Scotia was Gregorian 1605-1710, Julian 1710-1752 and Gregorian since 1752. Alaska became part of the US in 1867 and made the change then, except that the churches continued to use Old Style for a while.
Japan accepted in 1873, Russia in 1917 and 1940, China in 1949.
George Washington was born on 11 February (under the old calendar), but when he was an adult, his birthday was considered to be 22 February (under the new calendar). It is perfectly valid for an ancestor to have two birth dates, both of them correct.
All this was as confusing then as it is now, so original sources can be ambiguous. However, regrettably, as the International Genealogical Index has no facility for indicating Old Style/New Style notation, it creates ambiguities which were not present in original documents.
I've picked up the above facts all over the 'net, and hope that they all are accurate. --Beth
There are plenty of documents on the internet explaining
the issues surrounding these dates, with some links from the Date Converter
page (above), but here is one that I found useful http://www.fourmilab.com/documents/calendar/ with additional date
calculators.
You will also find more useful information from these links.
http://www.medievalgenealogy.org.uk/guide/chron.shtml
http://www.polysyllabic.com/CalHist.html
http://www.genuki.org.uk/big/easter/
The Julian Calendar
Before Gaius Julius Caesar (654--710 AUC, 100--44 BC) and the Julian
Calendar named for him, the Romans counted years of 355 days ab
urbe condita, from the building of the city of Rome. 1 AUC
is conventionally taken to be 753 BC, but as we shall see, the correspondence
between days and years was sometimes a little confused. Because the
Roman year was 10 days short with respect to the solar year, the start
of the year quickly got out of step with the constellations. The priesthood
arbitrarily added and subtracted days and even months which helped things
drifting too far, but even so, by 708 AUC (46 BC) the year
was well out of phase with the seasons.
For several years since his triumph over Pompey in 705 AUC
(49 BC), Julius Caesar had been in increasingly complete command of
Rome, regarded as semi-divine, and Emperor in all but name. Caesar
was
also a gifted astronomer, and well aware of the difficulties the existing
calendar caused. He decreed that 708 AUC (46 BC) should be
lengthened to 445 days in order that his new calendar be inaugurated
in step with the constellations on 1st. January, 709 AUC (45
BC). His new calendar had a year of 365 days plus a leap year every
fourth year with 366 days. This made the average length of the year
365.25 days, a good approximation to the real length of 365.24219
days,
and the Julian calendar continued almost unchanged for many centuries.
Julius Caesar's nephew and adopted heir, Gaius Octavian Augustus (691--767 AUC, 63 BC--14 AD) became first Roman Emperor in 727 AUC (27 BC) and renamed the month Quinctilis to Augustus and stole a day from February to give his month 31 days. The base date for the calendar was moved from the founding of Rome to various dates of local importance, and it was not until the 6th. century AD when the scholar Dionysius Exiguus made a study of Easter days that the Anno Domini epoch we now use came in to being.
The Gregorian Calendar
