The Dating Game

Well, y’all – time to play the dating game!  Before everyone thinks the poor old, dilapidated assistant historian lost his mental faculties, the dating game is not what one would think.  The dating game does not involve relative dating in neither a geological sense (and yes, I did say geological) nor a genealogical sense (with a subtle difference between the two).  I’m talking about double dating.  One could argue I may be referring to double dates as a genealogical phenomenon when two sisters date two brothers of a different family and may be related – ah, noooo, I’m not; at least, not in this case.

            The double dating I’m referring deals with calendrical systems.  For example 21 February 1721/22 is a double date.  Now why is there a slash between 21 and 22?  It has to be one or the other, but not both.  Well, yes and no.  Yes, in the sense it must be in a definitive temporal year, either 1721 or 1722; however, no because the two calendrical systems I refer to are the Julian calendar and the Gregorian calendar. 

            The Julian calendar started by Julius Caesar in 46 BC (https://en.wikipedia.org/wiki/Julian_calendar: accessed 19 July 2015) divided the year into 12 months with fixed 365 days with one day added every four years.  As time passed errors creeped in because of irregularity in earth orbit and lunar orbit throwing off religious festivals.  For example, Easter in the Christian Tradition occurred in the March timeframe.  As centuries passed the Easter date fell in the middle of May – far from March.  To compensate, Pope Gregory XIII introduced reforms.

            The Gregorian calendar is similar to the Julian except century years, 1800, 1900 (centuries divided by 100) are not leap years unless divisible by 400 (2000 is a leap year).  With the reforms, the calendars were brought into sync (https://en.wikipedia.org/wiki/Gregorian_calendar: accessed 19 July 2015).  The reforms instituted by Pope Gregory took effect 15 October 1582; however, Great Britain didn’t adopt it until 1750.  The American colonies didn’t adopt it until 1753.

            The example date I gave, 21 February 1721/22 means 21 February 1721 in the Julian calendar (Old Style) but 21 February 1722 in the Gregorian (New Style).  The double dates exist only between January-24 Mar (25 March is the New Year in the Julian calendar).  To add a further wrinkle, the Julian system is about 10 days behind the Gregorian meaning in the Old Style 21 February would be 11 February 1721, but 21 February 1722 in the Gregorian.  The trick is trying to keep the two systems separated.  For me, the best way to remember if there is a date with no slash for Jan-March, deduct 1 year and put a slash between the two years.