# Calculating dates over the calendar correction

+6 votes
228 views
Hi Cousins,

If the only source for dates of birth and death are a gravestone and, say, the birth date is calculable because chiseled on the gravestone is how many years, months, and days that person lived, how sure can I be if the length of life spanned before and after the correction of the calendar in the 1700s? If unanswerable, is the best I can do is to put an estimated date of birth without knowing what system of time the maker of the gravestone was using?

How many profiles would this affect? Hundreds? Thousands?

Thanks!

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## 4 Answers

+8 votes

http://mikesclark.com/genealogy/age_calculator.html

This is interesting. Give it a try cuz,

by Dallace Moore G2G6 Pilot (157k points)

Now that is cool, Dallace! I’m bookmarking that baby right now! Thanks!

+6 votes
I'm not sure how many profiles would be affected. I certainly haven't come across many gravestones that specify the age in months and days as well.

The biggest problem is that you have to make an assumption about whether the person who gave the information to the stonemason did or didn't count the missing days, and that's impossible to know now - although I'd bet most of them didn't take it into account.
by Suzanne Doig G2G6 Mach 3 (39.2k points)
+6 votes
I doubt if many took account of the date change in doing their calculation for the headstone. I would just calculate without it and add a note saying how you made the calculation.

A more likely cause of errors in our work around the period of the calendar change is where people have subsequently transcribed records with the wrong year after assuming that the year always changed in January. In working with images of parish records I see a lot of instances where the year on the transcript is wronf for baptisms in Jan-Mar.
by Lynda Crackett G2G6 Pilot (678k points)
+4 votes
Unfortunately, DMY ages can be ambiguous. There are two common ways to do it, one assuming that all the months are 30 days long and the other one using their actual lengths. If the calculation gives the same result either way, it's probably as reliable as ages at death usually are (which is not all that great), but if the result is different, it's hard to tell which method was originally used. Additionally, a lot of early arithmetic texts promulgate a 3rd method in which you take a month to be 28 days, but I've never seen evidence that these were used in epitaphs. There's also a potential difference between Julian and Gregorian calendars, but it doesn't come up much.
I wrote a long analysis of the problem many years ago with my own Javascript calculator,

http://www.buckbd.com/genea/bdexpl.html
http://www.buckbd.com/genea/bdjscr.html
by Living Buckner G2G6 Mach 5 (56.2k points)
Lynda and Ben both bring up another difficulty I hadn’t thought of. What if March 25th was bring used as the first day of the year. I realize that this is a little far fetched in more recent times, but in the Middle Ages or before, this could have been a lot more common.

Ben: good article!

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