We deal with approximate dates all the time in genealogy. I don't have a problem entering the rationale or the date in my software or writing about it in a narrative.

I'm working on a project now that involves some charting. Specifically, I'm displaying "life span" information. Ala, "Joe Smith (1699-1772)" or "Sally Thomas (1710-1781)." The question arises about how I should display date approximations that are unique when my presentation calls for a summary (year).

Each time I run into one of these "weird dates" I ponder whether or not there is some collective wisdom/recognized approach to summarizing the approximate dates as years.

enter image description here

As in the examples, it's sometimes the date and sometimes the circumstance that causes me to pause. For example, should I write 1723/4 to summarize the year for a double date 6 March 1723/4. In the alternative, should I consider the baptismal practices of the day? If the children were usually 6 months of more of age when they were baptized, should my summary then read 1723?

In the third example, since the parents were at court and punished--if I consider court calendars and birth practices, I might deduce the child was likely born four months earlier--so should the year be summarized as "1684?"

In the alternative, is the year summary always "just the year" from the approximated date.

I thumbed through some scholarly journals this morning, but did not spot an example that would have served as my guide. I'm not losing sleep over this but wonder if members of group have crossed the same path.

Update (clarity): I have revised the graphic/examples in the hope more specifics provide clarity. The problem I find is that my approximate date qualifier doesn't always hold when I move from using a specific date presenting it in some more summarized form (such note DD MMM YYYY but YYYY).

  • 1
    Why would #4, in and of itself, even indicate there was a marriage at all? Dec 11, 2012 at 22:58
  • 1
    @AndyHatchett In a vacuum, it wouldn't, but let's pretend.
    – GeneJ
    Dec 11, 2012 at 23:13
  • Am I correctly interpreting your question that you are asking is how to chart the ranges of uncertainty? Typically in math graph programs that is done with error bars.
    – Duncan
    Dec 12, 2012 at 4:58
  • @Andy - Maybe the parents were known to have been married when the child was born. Illegitimate children back then were hard to hide.
    – lkessler
    Dec 12, 2012 at 6:46
  • I have added an updated graphic and a few comments to the question. I hope this adds some clarity. Let me know if it is now officially as clear as mud.
    – GeneJ
    Dec 12, 2012 at 16:24

3 Answers 3


GEDCOM defines a date to handle the "weird dates" you show as examples. Any genealogy program that has implemented dates to the GEDCOM standard should allow you to enter all possible types of dates that GEDCOM allows.

Your examples would be stored in GEDCOM as:

2 DATE BEF 6 MAR 1723/24
2 NOTE Date of her baptism

As above, yes you should use double dates.

2 DATE 25 JUL 1735
2 NOTE On marriage record.
2 DATE 25 JUL 1736
2 NOTE On death record.

2 DATE BEF 2 APR 1685
2 NOTE Date both parents appeared in fornication court; punishment orderd.

2 DATE BEF 15 FEB 1821
2 NOTE Date their first child was born.

2 DATE BEF 5 MAY 1679
2 NOTE Date administration of his estate was opened.

2 DATE BEF 6 JAN 1789
2 NOTE His mother died on 5 JAN 1789.

"BEF" for "before" is just one of the GEDCOM date types allowed. There are date ranges (before/after/between), date periods (from/to), approximated dates (about, calculated, estimated), interpreted dates, and when all else fails you can use a date phrase (any text).

When deciding on what to actually specify as the date, I would use the narrowest range of dates that I'm certain will enclose the event, and give the reasons for them.

If I cannot specify the ranges, then I might estimate the date as closely as I can, and then document what I'm basing my estimate on.


I'm not totally clear what the question is. If a date is approximate, and has an upper and lower bound, then a simple plus/minus symbol would suffice ('±').

When dealing with inequalities (i.e. before, after, etc) in conjunction with approximate dates then there are rules for how to process the upper/lower bounds. See this table for instance.

I have to say that the era your samples are looking at, and the format used in the first one, suggests that they may be examples of Dual Dates. If so then these are not date ranges but rather the same point in time as measured in two different calendar systems (Gregorian and Julian).

  • I posted an updated graphic and added a few comments to the question. Please let me know if manages to make it clear as mud.
    – GeneJ
    Dec 12, 2012 at 16:23

This is not a "scholarly" suggestion but if I take your reference to charting to mean the production of graphics then you can display the window of uncertainty in a birth date like this: enter image description here

Obviously, the longer the person lived, the less obvious the initial slope will be compared to the total length. But if you can use a gradient fill, then it should be gently obvious that you do not have a definite date.

If you are planning to "calculate" life spans, then remember the mathematical principle that a derived quantity cannot be more precise than the least certain input. But also be aware that when we round age to a whole year, we may be creating an "error" that is larger than some of your uncertainties with respect to birth date.

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