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Using Date Standardization in Genealogy Research

Using Date Standardization in Genealogy Research

This is the first article in a three part series on standardization (dates, locations, names) but before I get started I want to present a few caveats. 

  • This series is from a United States viewpoint. Other countries have their own standards that might be a little different
  • These are data entry standards for genealogy software programs and not for formal genealogy reports
  • The reason you want adhere to generally accepted standards is two-fold:  1) When you create a gedcom to send to another person, or upload to a genealogy website, you want that person/website to be able to interpret your data properly and 2) When you are collaborating with other researchers you want everyone's data in the same format 
  • I can't cover every situation you might encounter because the articles would be book length
  • These standards are not set in stone but are generally accepted. It is your data and your file and you can format it any way you want. The one piece of advice I would give you is to be consistent with your data entry

There is one caveat specific to dates

  • I personally prefer to write everything out and forgo any abbreviations; however, standard abbreviations are acceptable. For example, you can abbreviate the names of the months to their standard three letter designations (Oct, no period) or you can abbreviate date qualifiers such as Before to Bef (or Bef. with a period). 

You want to format your dates with a two digit day, the name of the month spelled out and a four digit year so that there is no ambiguity, 04 October 1852. If you wrote 10-04-52  would that be October 4th or April 10th? Is it 1752 or 1852?

Surprisingly, FamilySearch prefers a one digit day (4 October 1852). I don't agree with them on this because without the first digit you will always wonder if a digit was accidentally left off (04 vs. 14 vs. 24).

There are some accepted date qualifiers you can use. 

About 1850 - Use About when you are fairly certain you are within a year or two

Estimated 1850 - Use estimated when you are basing your guess on some parameters. For example, if I estimate someone's marriage date based on the age of their oldest known child or I am estimating it based on the groom being about 21 and the bride being about 18, it is still a guess but I have considered some external data.

Calculated 04 June 1766 - The classic example of when you would use this one is when you have a tombstone that says, "Died 14 June 1843, Aged 41 years, 2 months, 12 days." You are going to calculate their date of birth based on the date of death and the age at death.

Before 06 October 1965 - Let's say you are looking at an obituary that says, "Proceeded in death by her sister Margaret." We now know that Margaret died before the person in the obituary did.

After 13 February 1850 - If Mortimer Simmons was a grantor or a grantee on a deed dated 13 February 1850 but you have nothing on him after that you can say that he died after the date of the deed.

Between 14 December 1809 and 25 January 1810 - If you have a combination of dates, a before date based on one document and an after date based on another, you can now narrow your date range. For example, if you have the date Beauregard  Simmons's will was written and the date the will was proved then Beauregard died between those two dates.

From 1850 to 1862 and 1850-1862 - These two are usually used interchangeably but they are slightly different. From 1850 to 1862 mean the event started in 1850 and continued up until 1862 but it technically doesn't include it. 1850-1862 is inclusive. It assumes the fact was true for the entire year of 1862.

Circa - This classic term has fallen out of favor but I still use it for captions on photographs because I think it looks cool. It is equivalent to About. For facts you need to use About.

There are other terms you will see with dates but these are normally used only in narrative reports and not with data entry into a genealogy database program (possibly, likely, probably, etc.)

There are four types of dates that need special treatment.

Quarter dates used in UK General Registry Office Records - For example March Quarter 1899 (or March Q 1899 0r Q1 1899). The event could have happened anytime during that three month period. You could write it as Between 01 January 1899 and 31 March 1899 but I like to just type it in with the Q because it is easily understood and takes up less space. Since many Americans have UK ancestry chances are you will see this. There are four quarters:

March Q (Q1)
June Q (Q2)
September Q (Q3)
December Q (Q4)

Court session terms are commonly used in court records - For example, Spring Term 1866. This one is trickier because which dates the term actually covered is a bit up in the air. It is different from jurisdiction to jurisdiction and in different time periods. You could use the date that the court record was signed or filed which covers all the cases during that term but just know that this date will not be exact for your particular case. I personally go ahead and record it as Spring Term 1866 which gives the general feeling of when the case would have been heard and it is something that most people recognize as a court term. This might trigger a date error in your genealogy software program but you should be able to override it. You might also see October Term which is much easier to deal with. You can simply record October 1879

Double dates - The accepted format for a double date is 04 February 1740/1. Every genealogy program I know of will double date for you. Not sure what double dating is? Learn about the 1752 calendar change from this article at the Connecticut State Library. One caveat. Unless most/all of the dates in your file refer to locations in Great Britain and its colonies don't let your genealogy program automatically double date for you. Other countries switched calendars on very different dates and it will really mess things up.

Quaker dates - The Quakers didn't use the names of days or months that were named after pagan gods and their dates were also affected by the switch from the Julian to the Gregorian calendar (double dating). If you were to record the date as they did, such as 12 iv 1731 or 12 4mo. 1731 (both are 12 June 1731), it just wouldn't be understandable to most people. You will need to convert these dates. For more information about Quaker dates, Swarthmore College has a very good article on the Quaker Calendar.

There will always be exceptions to the rule but the goal is to stay as standard as you can so that your data entry is consistent and it is understood by other researchers, other computer programs, and genealogy websites.


Slawson, Mary H. Getting It Right, The Definitive Guide to Recording Family History Accurately. Ann Arbor, Mich.: Malloy Lithographing Incorporated, 2002.

Though I don't agree with everything in the book, Mary has done a good job addressing some of the unusual situations you will come across. The book does needs to be updated but it still presents solid information.


Michele Simmons Lewis, CG® is part of the Legacy Family Tree team at MyHeritage. She handles the enhancement suggestions that come in from our users as well as writing for Legacy News. You can usually find her hanging out on the Legacy User Group Facebook page answering questions and posting tips.



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One thing you did not mention about quarter dates is that they are dates an event was registered, not the date it occurred. Events recorded early in the Quarter may have happened late in the previous quarter. My grandfather was baptized, according to church records, in late march of 1881 but his birth was not registered until the June quarter.

Excellent point!

Isn't the correct format for the years in double dates yyyy/yy? The year after the / is two digits. This is what the GEDCOM standard specifies. If a single digit is used it is not compliant with the standard.

YEAR_GREG:= {Size=3:7}
[ | / ]
The slash "/" a year modifier which shows the possible date alternatives for pre1752
date brought about by a changing the beginning of the year from MAR to JAN in the English
calendar change of 1752, for example, 15 APR 1699/00. A (B.C.) appended to the indicates
a date before the birth of Christ.

I went for a good long while, foolishly assuming "Cal" in a certain work was just a misprint of "Ca" for circa, which I guess is another point in favor of switching my habit to About/abt. !

A lot of these doubts could be clarified by using the format YEARMODA (example: 20180724) with or without spaces or dashes in between YEAR MONTH DATE. It also automatically organizes the files in ascending or descending order in your computers

England & Wales Registration Quarter Dates.
For Births and Deaths these are the quarters of Registration, NOT the quarter of the actual event.
42 days [6 weeks] are allowed for registering a birth.

Maybe but that format is non standard :)

@Michele: - respectfully, I disagree with "that format is non standard". The international standard, ISO 8601, specifies that YYYY-MO-DD (or YYYYMODD) is indeed the standard for calendar dates. See

It is not a non-standard date format when you are looking at all the different types of date formats that possible. As a matter of fact, I use this reverse order in Excel spreadsheets all of the time, though I do hyphenate it. However, it is non-standard when it comes to input into genealogy database programs. It is also non-standard for narrative reports and published articles.

See the first comment in the list of comments. I should have mentioned that these are registration dates but Brian beat me to it :)

Genealogy database programs put a single number after the slash.

The author says at the beginning that this series is from a United States viewpoint. Not surprising therefore that the International Standard is ignored!
Gene Chan hits the nail on its head.
If there is to be date standardisation, why not use the established international standard?

Actually it's the US that is non-standard (and in my view nonsensical) in its date format. The ISO format is big-endian, ie smallest thing at the end. The normal date format is little-endian, ie the largest thing at the end.

The US has middle thing, smallest thing, largest thing as its date format: erm what?! It's also extremely ambiguous. What is 6/12/2018? 6th December 2018 is what the vast majority of the world's population will say. 12th June 2018 is what Americans, and pretty much no one else will say. I really don't know why the US formats its dates like it does. I can't think of a logical reason for doing so, and so I must conclude that the reason is illogical.

As for leading zeros or not, that's a matter of presentation rather than fundamental storage. I'm also really not sure why you mention the GEDCOM format. It's 22 years old and obsolete, and most importantly it has never had a proper, bug-free implementation in any case. Direct interface to major genealogy websites via an API is the way forward in terms of sharing data and GEDCOM will be left to wither on the vine. Quite a few of the remaining desktop genealogy programs are moving to support direct API interfacing if they don't have it already. Frankly I think that there's going to continue to be a winnowing of desktop genealogy program and that those which don't support direct API access will be more likely to go down. Legacy Family Tree has moved in that direction itself with Familysearch integration for example.

From the outset I said this was coming from a US perspective. I mention gedcoms because that is what we have to work with. Nothing would make me happier than the gedcom protocol being updated. All genealogy programs have gone way beyond its capabilities and they end up using custom tags that other programs don't necessarily understand. There have been "movements" in the past to get the gedcom updated but so far nothing has happened.

I made it clear this was from a US perspective. It would be impossible for me to go through and cite what every country prefers because there is no "international" consensus. I work a lot with German records and German researchers. What they do is totally different than what the UK does. I will say that most countries feel the US goes "overboard" with source citations. That is one of the areas that we differ.

I believe "Quaker Dating" is a misnomer. Quakers used/use the calendar in use by their location at the point in time. As you indicate, the Society of Friends wrote/write the number of the month instead of the name. When the American Colonies were using the Julian Calendar until 1 Jan 1752, the recording clerk of the Meeting knew the 6th day of the 12th month 1749 was 6 February 1749/50. Quakers writers also knew some countries were already using the Gregorian Calendar so they double dated the year for the months of January, February & March.
Your presentation says, "You will need to convert these dates." Instead of converting the Julian dates to the Gregorian Calendar, I believe pre 1752 dates need to simply be transcribed with the name of the month as above. Your thoughts?

Sometimes they did double date but many times they did not. You will need to supply the double date. The biggest issue is that they used numbers for the months based on the old calendar. That is where it gets confusing.

Needing to use the ISO standard here. Can you tell which genealogy programs allow that? RootsMagic does not, we find after purchasing.

ISO standards are not related to genealogy. Having said that, if you send me an email at [email protected] and put Attn: Michele it will get to me. If you tell me exactly what you are trying to accomplish I will be able to tell you if it is possible in legacy.

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