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Estimating Dates

Genealogy Essays:

Recording Adoptions
How do you draw adopted children in a family tree? (2011)

Those Elusive Edes
9 lessons learned about finding people in the census. (2009)

The Joys of Inveterate Button Pushing (2004)

Who's Your Daddy?
Genealogy versus family history. (2004)

Suspicion Meters
Your program doesn't have one, but you do. (2004)

Estimating Dates (2002)

A cautionary tale (2002)

Count Your Blessings
1988 and now (2002)

The Grand Chase
How my individuals connect (2002)

What makes a family? (2001)

A genalogical detective story (2000)

Eben J. Cady
Musing about a tombstone (2000)

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(Parts of this appeared in:
Missing Links: A Magazine for Genealogists
The Petunia Press
Volume 7, No. 34, 26 August 2002;
Volume 7, No. 35, 01 September 2002;
GenForum.com General Topics post on 23 June 2002)

A lady on GenForum asked "Is it preferable to use 'circa' rather than 'about' when making reference to a date?"

I think a range and a note are much more useful than either term. For instance, consider "about 1850." If it is a birth year estimate derived from someone being 20 years old on the 1870 census, it means "1849 - 1850." If it is a birth year estimate for someone with nine siblings, birth order unknown, whose parents married in 1838 at age 20, it could mean "1838 - 1862." If it is an estimated death date for someone who left home at the age of 20 in 1801 and was never heard from again, it means "1801 - 1884." He may have drowned crossing the river six miles from home. He might have made it to Ohio, stolen 160 acres of rich bottom land from the Indians and lived to be 103.

Note 1, if great uncle Hezekiah is 20 on the 1870 census, I'd estimate his birth year as 1848 - 1852, just to include all the possibilities. Age on the census is not always accurate.

Note 2, a range ("1849 - 1851") will not always work. See below if your genealogy program will not allow a range in the date field.

We all estimate birth and marriage years. It helps to winnow out the prospects when you are trying to make connections or wade through online databases. If my Ebeneezer was born 1791 - 1793, he could be the father of your Samuel, who was born 1814 - 1834. Ebeneezer couldn't be the father of anyone born before 1804, and it is unlikely that he is the father of anyone born after 1850. If you publish your work, on paper or on the Web, using a range and a note instead of "abt" tells people where the estimate came from and how accurate it is. It will tell you, too, if you put that line down to chase someone else for a couple of months.

If Mortimer Periwinkle is 25 on the 1850 census, 35 on the 1860 and 45 on the 1870, there is a good chance he really was born 1824 - 1825. On the other hand, if I have Eltweed Pomeroy born 1810 - 1830 based on his marriage to a woman who was born in 1820, I know there is a good chance he was born earlier than that; if I find an Eltweed born in 1800, I'll investigate.

There is one danger in using a range; if you neglect the note, people may think it is exact. A man who married in 1843 and died at Gettysburg would have to have children born 1843 - 1863, not counting any who sprouted earlier from his wild oats. (He could have a child born early in 1864, if he got a home leave before the battle.)

A woman who married at age 20 in 1843 would normally have children born 1843 - 1863, but she could bear a child in 1868. So - add the note.

I use these ranges for estimating birth and marriage years. I have exceptions to every one of them. Genealogy wouldn't be as much fun if you didn't get to take wild guesses now and again.

  • Spouses in first marriages are born within 10 years of each other.
  • Spouses in first marriages are between 16 and 32.
  • Women bear children from age 16 to 40. (This is my most frequent exception; some pioneer women gave birth at 46 and others at 14.)
  • Siblings are born within 24 years of each other.

An interesting thing to do along these lines is look at the birth years of an entire generation of ancestors. Print or display a five- generation pedigree chart, then look at the great great grandparents. I just did it for my daughter. Her great-great-grandfather CADY is an exception, born in 1837. However, 14 out of 16 of her great-great grandparents were born in a narrow range, from 1854 to 1871. The last GGP's birth year is unknown, but I have a pretty good estimate for her; within 17 years, at least.

(I wrote this next part for the next issue of Missing Links, after a deluge of e-mail messages.)

When I was a boy, growing up in central California, I thought the rest of the world was pretty much like the one I knew. It rained once or twice in the summer, which started in April and lasted until October. Winters were mild, and snow was something they used to have long ago, like cowboys and Indians. The Courier and Ives prints my mother favored may have encouraged my misapprehension. Lots of them showed snow, but all the men in the pictures had mutton-chop whiskers and all the ladies had high-buttoned shoes.

I grew up and I traveled. Summer never leaves in Borneo, and it rains every day or two. Summer starts a little later than April in New Hampshire. I fear a bit of that childish wonder is still with me, however. In my article, "Estimating Dates", I blithely assumed all genealogy programs would accept all dates, just like mine does. I've used "Family Origins for Windows" for years. It isn't as popular as Family Tree Maker, as advanced as The Master Genealogist or as cheap as PAF, but it does the job for me. It accepts date ranges, be they long ("1819 - 1843") or short ("1824 - 1826"). It accepts "4004 BC," if you get back to Adam. It even accepts "2 gen bef 1412," which means "2 generations before 1412."

Note 3, FOW is gone, suceeded by Roots Magic, which still accepts a date range.

A number of kind and learned people wrote to me, telling me that my ranges won't work in other genealogy programs. So, if I send a GEDCOM to someone who doesn't use FOW, or transfer my data to a new program, all of my carefully calculated ranges may be lost. Virtually all programs will handle "Abt," however, which is why so many people use the term. (Like driving a dull nail through a thick plank, wasn't it?) The best way to handle date ranges for some programs is to use "Abt," and put an explanation in the note field for the individual. To take one example, if a man was born in 1850, his first wife was probably born 1840-1860. Eight times out of ten, in my family, she was born 1849-1854. "Abt 1852" would be a good birth year for her, with a note saying I had estimated her birth year from her husband and any year between 1840 - 1860 would be possible. (Unless, of course, their first child was born in 1870.)

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This page updated: June 21, 2014