How to write dates in genealogy
Short answerGenealogists write dates as day, month, year with the month as a word, for example 3 March 1921, so they can’t be misread across countries. Uncertain dates are marked about, before, after or between (ABT, BEF, AFT, BET in GEDCOM). Dates from 1 January to 24 March before the calendar change are often written with two years, such as 14 February 1699/1700.
Why day month year
03/04/1921 is 3 April in Britain and March 4 in the United States. Writing 3 April 1921, with the month as a word and the full four-digit year, means the same thing to everyone, and it’s the order GEDCOM files use (3 APR 1921).
Approximate and uncertain dates
| You know | Write | In GEDCOM |
|---|---|---|
| Roughly when | about 1890 | ABT 1890 |
| A worked-out estimate | estimated 1890 | EST 1890 |
| A worked-out figure, e.g. from an age | calculated 1890 | CAL 1890 |
| It was before a date | before 1890 | BEF 1890 |
| It was after a date | after 1890 | AFT 1890 |
| It falls in a range | between 1885 and 1890 | BET 1885 AND 1890 |
| Only the year, or month and year | 1890, or March 1890 | 1890, MAR 1890 |
Never turn a guess into an exact date. “About 1890” tells the next researcher where to look; a made-up 1 January 1890 sends them the wrong way.
The Julian to Gregorian switch
Pope Gregory XIII introduced the Gregorian calendar by a papal bull of 24 February 1582. Catholic countries such as Spain, Portugal and the Italian states moved that year, dropping ten days so the spring equinox fell on 21 March again. Other countries moved later. Britain and its colonies, including the American colonies, changed in 1752 under the Calendar (New Style) Act 1750: Wednesday 2 September 1752 was followed by Thursday 14 September, skipping eleven days.
The same change moved the start of the year. Before it, England counted the new year from 25 March, so 24 March 1700 was followed by 25 March 1700, and January 1700 came after December 1700 in the old reckoning.
Double dating
For dates between 1 January and 24 March in the years before the switch, records may give either year. Genealogists write both: 14 February 1699/1700 means 1699 in the old (Julian, March new year) reckoning and 1700 in the modern one. The FamilySearch Research Wiki recommends double dating for this window between 1582 and 1752. Copy dates as written in the record, then add the second year; don’t silently “correct” them.
Other calendars you may meet
- Quaker dates use numbers for months (“3rd day of 1st month”). Before 1752, the first month was March.
- The French Republican calendar was used in France from 1793 to 1805, with its own month names and year numbers.
- Hebrew, Islamic and other religious calendars appear on gravestones and religious records. Note the original date alongside the converted one.
Doing this in Family Trees
Family Trees stores dates you know only partly, such as a year or a month and year, and marks approximate dates. When it imports a GEDCOM file, dates written as before, after, between or about are kept as approximate dates. See the GEDCOM guide.
Questions
How do you write an approximate date in genealogy?
Write “about” before the year, for example about 1890, or ABT 1890 in a GEDCOM file. Use before, after or between when the records give you a limit or a range.
What does 1699/1700 mean on a family tree?
It is a double date. Before the calendar change the year began on 25 March, so a date in January to March can belong to 1699 in the old reckoning and 1700 in the modern one. Writing both avoids confusion.
When did Britain and the American colonies switch to the Gregorian calendar?
In 1752. Under the Calendar (New Style) Act 1750, Wednesday 2 September 1752 was followed by Thursday 14 September, and from 1752 the year began on 1 January.
Why do genealogists write the day before the month?
Day month year with the month spelled out, like 3 April 1921, can’t be misread in any country. Numeric dates such as 03/04/1921 mean different days in Britain and the United States.
Sources
Links go to other sites. Checked 19 October 2026.
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