If you ever decide to do some looking into your family history, and you make it back to, say, the early 1700s, you will probably see one or more dates written like this: Jan 7, 1719/20. Unlike what you might think, that doesn’t mean the author was unsure of what year the event happened in, so they wrote both; rather, it indicates the event occurred on Jan 7 of… either 1719 or 1720, depending on whether you go by the contemporary calendar of the time, or our modern calendar today. And, making matters worse, it was not a Jan 7 that was an even number of years removed from this year’s Jan 7. Worst of all, it may also have reflected a culture that didn’t acknowledge the new year until the end of March. March?
I know, “clear as mud.”
If you’re scratching your head at all this, the problem stems from a major disruption in the measurement of time that occurred when Europe, and Europe’s colonies, switched – slowly, over several years – from the calendar that had been employed by the Romans, aka the Julian calendar, to an updated system, adopted by Pope Gregory, aka the Gregorian calendar.
This is not a minor point.
It affects the citation of all “early” colonial historical dates in a meaningful way, and the explanation below is, I’m sorry to say, actually worth wading through…
The Julian and the Gregorian Calendars
by Peter Meyer
The Gregorian Reform
The average length of a year in the Julian Calendar [the calendar put in place by Julius Caesar] is 365.25 days (one additional day being added every four years). The length of the year in the Julian Calendar exceeds the length of the mean solar year (365.24219 mean solar days to five decimal places) by 11.2 minutes. This error accumulates so that after 128 years the calendar is out of sync with the equinoxes and solstices by one day. Thus as the centuries passed the Julian Calendar became increasingly inaccurate with respect to the seasons. This was especially troubling to the Christian Church because it affected the determination of the date of Easter, which, by the 16th Century, was well on the way to slipping into Summer.