Here's an example, from the parish records for Merioneth/Meirionnedd in north-west Wales:
It looks as if nobody was baptised, married or buried between March 21, 1748, and March 25, 1749 - which isn't very likely. But not understanding this record could cause problems.
Suppose you're looking for Hugh Ellis and all the evidence points to him being born in Cae Gwernog in 1749 - and you found this record. You might think your other information was wrong, because it looks as if he was baptised on 21 April, 1748.
You might find a parish record which is even more puzzling (but gives a clue to the solution), like this one for the baptism of Mary Roberts of Tarporley, from the Diocese of Chester parish records:
She was baptised on 1 January, 1744. But wait a minute - just above her in the baptism of Thomas Garnett, on 30 December... 1744. Couldn't these people keep their records in order?
And yes, of course, they could. It's just that the calendar was organised in a slightly different way until 1752 in Britain and its colonies.
Old StyleFrom the late 12th century until 1751, the legal year began on Lady Day, the Feast of the Annunciation, celebrated on 25 March (exactly nine months before Christmas Day). So the year changed on that day: 24 March, 1750, would be followed by 25 March, 1751, and the year's length was calculated according to the Julian calendar. It seems odd to us, but since it was the way things had been for centuries, it was easy to understand.
New StyleExcept that in October 1582, Pope Gregory XIII introduced a new calendar. By then, because the length of a year under the Julian calendar had been slightly over-calculated as being 365 days and six hours, with the six hours being added together every fourth year to make a leap year, the date of Easter had drifted too far away from the Spring equinox.
This also resulted in 'removing' 10 days from the calendar to make up for the drift. The new calendar, known as the Gregorian, was adopted by Catholic countries. But the English-speaking world was officially Protestant, and Protestant states weren't having anything to do with a change decided by the Pope. They stayed with the Julian calendar.
This caused confusion in dating letters, reports and documents which crossed the time zone between Protestant and Catholic countries.
To avoid this confusion, people often dated their papers using OS (Old Style) and NS (New Style), or gave two alternative years for those awkward days from 1 January to 24 March, like 1700-01, or 1700/1.
Here's how one newspaper, the Newcastle Courant, coped with the date problem:
You'll notice that in the latest edition the paper is dated 1744, but the first article mentions a date as being in OS - it's a report from (Gregorian, NS) France.
Just to add a little more confusion, the legal year in Scotland was changed to begin on 1 January in 1600, and after the Union of Parliaments in 1707, this caused more legislative problems.
Parliament wasn't happy. In 1750, it stated that the use of the Julian calendar was 'attended with divers inconveniences, not only as it differs from the usage of neighbouring nations, but also from the legal method of computation in Scotland, and from the common usage throughout the whole kingdom, and thereby frequent mistakes are occasioned in the dates of deeds and other writings, and disputes arise therefrom.'
And so the Calendar (New Style) Act 1750 was passed. It ruled that the English-speaking world would make two changes in 1752: that year would start on 1 January everywhere; and there would be 11 days removed from the calendar, since the drift had widened another year since 1582, when the Gregorian calendar came into force.
Still with me? Phew! I think we both deserve a picture to help explain the effect this had on record-keeping.
These are burials from the parish records of St Stephen's Church in Norwich. You'll see that 1750 burials go from 31 March to 14 March; 1751 burials are from 25 March to 24 December; and 1752 burial start on 2 January.
The other part of the changes brought about by the Calendar (New Style) Act 1750 was the removal of 11 days. Here's the law:
The Whitehall and General Evening Posts tried to explain the whole muddle on the morning of 14 September, NS:
Until recently I believed the story that the loss of 11 days caused widespread riots, with people furiously demanding: 'Give us back our eleven days!'
Unfortunately, it seems that this is an urban, and rural, myth, though the phrase was well enough known at the time. It appears, as 'give us our Eleven Days', on a placard at the bottom of William Hogarth's satirical painting An Election Entertainment:
But the missing 11 days isn't just a story about how daft the uneducated people were. A very recent blog post has pointed out that, though poorer people's wages, which were often paid by the day, fell by a third in September 1752, their rents did not. A good reason to be angry.
The taxes still had to be brought in, and so (rather than lose 11 days' tax) the government ruled that the new fiscal year should start 11 days later than Lady Day. And an extra day was added in 1800. That's why the UK tax year begins on 6 April - it's the old Lady Day, plus the (now) 12 days' drift.
Finally, as everyone's going Shakespeare mad, with the 400th anniversary of his death on 23 April, here's a brain teaser:
Shakespeare and Miguel de Cervantes died on the same date - but not on the same day. How can that be?
Notes:Believe it or not, I've simplified things a lot here. The original Calendar (New Style) Act 1750 can be read online, if you really want to
All images are from FindMyPast, except for the Hogarth painting, An Election Entertainment, which is CC via Wikimedia, and the extract from the Calendar Act
If working out OS/NS dates is too much of a time-waster, there's a handy online date converter to do the work for you