Double Dating
What Is Double Dating?
Double dating is not a clerical mistake. It was a practical way of acknowledging that the same day could belong to two different numbered years depending on which calendar convention was being used.
1699 reflects a year that did not end until 24 March, while 1700 reflects the system in which the new year had already begun on 1 January.
For genealogists, this matters most when a date falls in January, February, or 1–24 March. A difference of one year may have nothing whatsoever to do with an inaccurate record.
Two Different Date Traps
Historical dating becomes much easier once we separate two changes that are often bundled together.
When Did the Year Begin?
In parts of Britain the legal or official year once began on 25 March rather than 1 January. That means January, February, and the first twenty-four days of March could be assigned to what a modern researcher considers the previous year.
Which Calendar Counted the Days?
Britain continued using the Julian calendar long after some European countries had adopted the Gregorian calendar. The same historical day could therefore carry a different day-and-month date in different places.
Calendars Old & New
The older calendar used in Britain was the Julian calendar. The Gregorian calendar was introduced in parts of Europe beginning in 1582 because the Julian system had gradually drifted away from the solar year.
Britain did not formally adopt the Gregorian calendar until 1752.
Julian Calendar
The calendar traditionally used in Britain before the reform of 1752.
Gregorian Calendar
The reformed calendar introduced in continental Europe beginning in 1582 and adopted in Britain in 1752.
OS & NS
Historical works may label dates OS (Old Style) or NS (New Style). Always check what the writer means by the notation rather than assuming the date has already been converted for you.
Location matters. Before interpreting an early date, ask where the record was created and which calendar convention was in use there at that time.
When Did the New Year Begin?
To a modern reader, the year changes automatically after 31 December. That was not always the official convention.
Before 1600 in Scotland, the official year began on 25 March. The date immediately before it was still part of the previous numbered year.
The day and month have not changed in this example. Only the year number has been expressed according to the modern January-to-December year.
This can create very real genealogical confusion. A baptism in February 1577 followed by another event in April 1578 may appear more than a year apart to a modern reader when they may actually have occurred only weeks apart.
Scotland & England Did Not Change Together
This distinction is particularly important for Scottish genealogy because Scotland changed the beginning of its official year long before England did.
Scotland
James VI ordered that Scotland begin the year on 1 January from 1600.
Scottish records after that change normally use the familiar January-to-December year numbering.
Scotland nevertheless continued using the Julian calendar for day-and-month reckoning until the British calendar reform of 1752.
England
England continued to reckon the official year from 25 March through 1751.
The beginning of the year moved to 1 January in 1752.
Between 1600 and 1751, a January, February, or early-March date could therefore belong to one numbered year in an English record and another in a Scottish record.
The date could be regarded as February 1699 under the old 25-March year reckoning, but February 1700 under the January-to-December system already used in Scotland and familiar to us today.
The Missing Days of 1752
Britain finally adopted the Gregorian calendar in September 1752.
By then an adjustment of eleven days was required.
2 September 1752
14 September 1752
No one lost eleven days from his or her actual life. The numbering of the calendar was corrected so that Britain would use the Gregorian reckoning already followed elsewhere.
This also explains why researchers comparing British records with records created elsewhere in Europe may encounter differing day-and-month dates for the same historical event before Britain adopted the Gregorian calendar.
How Should You Record the Date?
The safest approach is to preserve what the original record says while making your interpretation visible.
Transcribe the Original Date Faithfully
If the document says 1 February 1699/1700, preserve that double date in your transcription.
Identify the Dating Convention
Determine where the record was created, whether the year began on 1 January or 25 March, and whether the date uses Julian or Gregorian reckoning.
Standardize Only When Useful
A modernized date can make chronology easier to understand, but label the conversion rather than silently replacing the original.
Leave a Note
Explain why the record and your standardized tree date appear different. Your future self—and anyone copying the research—will know that the discrepancy was intentional.
A Useful Way to Preserve Both
When two records disagree by exactly one year—or by a familiar calendar offset—check the calendar before deciding you have two different people.
Before You Change the Date, Check the Calendar
A date that looks wrong may be telling you something about the calendar, not the ancestor. Preserve the original wording, identify where and when the record was created, and distinguish year-number changes from Julian/Gregorian calendar changes. Sometimes the apparent contradiction disappears as soon as you understand which calendar was doing the counting.