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Doubling up on dates

When exactly was the first day of 1751?

That’s not a trick question.

The Legal Genealogist isn’t out to flummox anybody.

But if you’ve got an event in your family history that occurred on the first day of 1751, figuring out when exactly it occurred may not be quite as easy as it appears.

google-doodle-datesYesterday’s Google Doodle would give you a hint of the problem.

Go ahead and click on the image here if you haven’t already gone ahead and looked at it.

It’ll tell you that yesterday, October 4th, was the 434th anniversary of the adoption of what came to be called the Gregorian Calendar.1

It was, the Google Doodle explanation tells us:

part of a realignment of the Julian calendar, implemented by Julius Caesar in 46 B.C. In the mid-1570s, it was discovered that the Julian calendar was actually 10 days behind the seasons of the year. For example, Easter began falling later in the spring than it should have and eventually would have drifted into summer. The calendar creep was the result of the solar year (the time it takes Earth to make one revolution around the sun) being around 11 minutes shy of the full Julian calendar. To be precise, the solar year is actually 365 days, 5 hours, 48 minutes, and 46 seconds.


Pope Gregory saved the day (and season) by appointing a commission to solve the problem. It took five years, but eventually the group, led by physician Aloysius Lilius and astronomer Christopher Clavius, proposed eliminating three leap years every 400 years to keep the calendar on track. To transition to the Gregorian calendar, ten days were declared officially non-existent, with the day after October 4, 1582 declared October 15th. First implemented by Italy, Spain, and Portugal, the Gregorian calendar is today’s most widely used system.2

And therein lies the problem.

Because even though it’s “today’s most widely used system,” it wasn’t adopted everywhere at the same time.

Particularly problematic for those of us who descend from the English colonial system, the Gregorian calendar wasn’t adopted in England until the adoption of the Calendar Act of 1750.3

Yeah, that means exactly what you think it means.

From 1582, when the Gregorian Calendar was declared effective, until 1752, the first day of the year was different between England (and its colonies) which followed the old Julian Calendar and the continental countries where the Gregorian Calendar was followed. And the dates didn’t match up anyway.

Start with the first day of the year issue. In the Gregorian Calendar, it was January 1, and that’s what England went to in 1752. 4 But before then? It was March 25th. So, to bring the calendars into alignment, “In England and Wales, the legal year 1751 was a short year of 282 days, running from 25 March to 31 December. 1752 began on 1 January. … the calendar was advanced by 11 days: Wednesday 2 September 1752 was followed by Thursday 14 September 1752.”5

So when exactly was the first day of 1751?

I get to give my favorite answer: it depends.

If it was England, it was still 25 March 1751. If it was, say, Italy, it was January 1.

Now let’s say you have something that occurred in 1751. Say, just for the sake of argument, that there was a bright meteor that flashed across the sky, visible on just one single day, from England to Italy.

If it was recorded as visible in Italy on the first day of 1751, when was it visible in England?

It wouldn’t have been January 1 in England. It wouldn’t even have been close to January 1 in England.

Because of the mismatch in dating under the calendars, January 1, 1751, in Italy (Gregorian Calendar) would have been December 21, 1750, in England (Julian Calendar).6

If it had been January 1 in England, it would have been January 12 in Italy — and the English date would be recorded today (and might well have been recorded at the time) as 1750/1751 (or 1750/51 or 1750/1), the dual dating reflecting the fact that it was 1750 legally but 1751 on the solar calendar:

Between 1582 and 1752, not only were two calendars in use in Europe (and in European colonies), but two different starts of the year were in use in England. Although the “Legal” year began on March 25, the use of the Gregorian calendar by other European countries led to January 1 becoming commonly celebrated as “New Year’s Day” and given as the first day of the year in almanacs.


To avoid misinterpretation, both the “Old Style” and “New Style” year was often used in English and colonial records for dates falling between the new New Year (January 1) and old New Year (March 25), a system known as “double dating.” Such dates are usually identified by a slash mark (/) breaking the “Old Style” and “New Style” year, for example, March 19, 1631/2. Occasionally, writers would express the double date with a hyphen, for example, March 19, 1631-32. In general, double dating was more common in civil than church and ecclesiastical records.7

Fun, huh? It’s not enough that we have to go chasing every Henry in town to figure out which one is our Henry, but we also have to figure out what year … or even day … an event took place…

It’s all a matter of time.


  1. October 4, 2016: 434th Anniversary of the Introduction of the Gregorian Calendar;” Google Doodles ( : accessed 5 Oct 2016).
  2. Ibid.
  3. “An Act for Regulating the Commencement of the Year; and for Correcting the Calendar now in Use,” 24 Geo. 2 c. 23, in Danby Pickering, Statutes at Large from the 23rd to the 26th Year of King George (Cambridge : Joseph Bentham, 1765), 186; digital images, Google Books ( : accessed 5 Oct 2016).
  4. See Matt Soniak, “Why Does the New Year Start on January 1?,” MentalFloss, posted 31 Dec 2011 ( : accessed 5 Oct 2016).
  5. Wikipedia (, “Calendar (New Style) Act 1750,” rev. 12 Sep 2016.
  6. See Stephen P. Morse, “Converting between Julian and Gregorian Calendar in One Step,” calenculation for Gregorian date 1751, January 1, One-Step Webpages by Stephen P. Morse ( : accessed 5 Oct 2016).
  7. The 1752 Calendar Change,” Colonial Records & Topics, Connecticut State Library ( : accessed 5 Oct 2016).
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