# (+) Calculating Birth Dates from Death Date Information

The following is a Plus Edition article, written by and copyright by Dick Eastman.

What day was that ancestor born? It seems like such a simple question, and yet finding the answer can be surprisingly complex, even when you have the numbers in front of you. Exact dates are often found in death certificates and frequently on tombstones. The problem is that these are often written as death dates followed by the person’s age at death.

Here is a common example:

Here lies the body of John Smith,
Died August 3, 1904,
Aged 79 years, 9 months, 29 days

How do you tell John Smith’s date of birth? You obviously need to subtract 79 years and 9 months and 29 days from the date of death. Simple, right? Well, not as simple as it first appears.

First, was it a 31-day month or a 30-day month? Or was it 28 days or 29 days in the case of February?

Next, you have to calculate in Leap Years. Everyone knows that Leap Years occur every four years; but did you know that there is an exception every 100 years? And, just to complicate matters more, there is an exception to that exception every 400 years? Then there is the issue of which calendar was in use. Was it the Julian calendar or the Gregorian calendar?

There are easy solutions to the question.