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Double Dating Like a Genealogist

old calendar

September 18, 2019

You could ask someone out on a date and bring another couple to a program at the Midwest Genealogy Center, but that’s not exactly what I meant by double dating. Sometimes in genealogy, you will come across an old date that looks something like this: 13 Jan 1718/19. It doesn’t mean that a person was unsure what date the event happened, but that two different calendar systems were once used.

For centuries, most of the Western world used the Julian calendar, but gradually the days were no longer coordinated with equinoxes and solstices. The Gregorian calendar was introduced in 1582, but it took more than 300 years for some countries to adopt it. Turkey did not adopt it until 1927! Genealogists often use “double dates” to specify both Old Style (O.S.) and New Style (N.S.) dates.

Not everyone was happy about changing from one calendar to another. In 1752, England switched from the Julian calendar to the Gregorian calendar. In the Julian calendar, the official start of the year was March 25, known as Lady Day; so 1751 began on March 25 and ended on December 31, making that year only 282 days.

Since most of Europe had been using the Gregorian calendar already, Britain had to gain 11 more days. They decided that September 2 would be followed by September 14. Some people were angry and demanded that the government “give us our 11 days back.” Could you image how we would react today if we had to make that kind of change?

Next time you are looking at early British records or Colonial American records, don’t forget the calendar system. You might end up looking for a genealogy record in the wrong year if you are not careful. The Library has some great books on dates and calendars for genealogists. Check out Genealogical Dates: A User-friendly Guide by Kenneth L. Smith, and soon you will be double dating like a genealogist!

Jolene C.
Midwest Genealogy Center

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