November 11th, 2011

Estimating the Date of Your Ancestors Birth

Finding dates for births, deaths and marriages before Civil Registration was enacted can be a tedious and time consuming endeavour. Most Civil Registration wasn’t enforced until the mid 19th century, and often researchers are left scratching their heads as to what to do or where to look next when tracing ancestors who were born, married or died before those times. True there are Parish Registers, Census Reports, and Newspaper Archives to look through, Military Records and Ship Passenger lists and the like, but if you have no idea of the subject’s birth date or even age, it is impossible to know what time frame to look for those records in. In such cases it may be necessary to estimate the time of the particular event you’re searching for. As each event has its own particular complexities, we’ll designate a unique Blog to each, beginning with in this one; Birth Dates.

Tricks to Estimating the Date of Birth

There are several tricks that researchers use to estimate unknown dates, and these include; inferences, approximations, processes of elimination, and a knowledge of human behaviour as well as social and legal customs of the period. Considering these things will help you to narrow down the required date. Let’s look at a few of these options individually to get a clearer picture of exactly how they can be applied.


If you count backwards from the time of the last known marriage date or birth date of a first child you may have, say for your grandparents, you can approximate the birth date for your great-grandparents. Generally speaking, eighteen to twenty years is a good rule of thumb for a woman’s first marriage, and twenty to twenty eight for a man’s. Those who lived in rural areas may have married even younger, so it may be helpful to know what the occupations of your grandparents were, if not subtract two years less for both sexes (women 16-23, men 18-28).


The age at which a woman stopped having children may also be used to approximate her age, and consequently birth period. It is very rare for women, especially in previous generations, to give birth after the age of forty five. If she does stop, and then after a period of three years or more, another child appears in the record, there are three reasons this may have occurred – these would be inferences.

  1. The first possibility is that the woman was caring for a grandchild (to conceal the illegitimate birth) or caring for an adopted child.
  2. Secondly, she may have had a menopausal child. In such cases there was a greater chance of the child having Down’s Syndrome, so stay alert to Census reports that list the child as “defective”, “void of intelligence”, or “dependent”.
  3. The third instance is that she is the second wife of the male, possessing the same forename as the first wife. This happened fairly frequently, especially before the mid-nineteenth century, and consequently such women are hard to track genealogically. If a significant period of time passes with her not appearing in the records and then she suddenly surfaces again, there is a good chance that such is the case. Believe it or not, and I found this most amusing, many men married women with the same name to avoid the embarrassment of saying the wrong name during intimate moments. There is one example, a certain James Beall a delegate to the Kentucky Secession Convention who erected a tombstone in memory of his three wives – all named Sarah!

Social and Legal Customs

The legal age of consent is also important in the estimation of birth dates, and therefore it is critical to have some knowledge of the laws of the particular community during that period. And this includes more than the age of consent for sex. For instance; in some places individuals could not purchase land until they were twenty one years of age, while in colonial times, a child of fourteen could legally choose their legal guardian. This is genealogical knowledge that can really speed up research. Id a person is a registered land owner for instance, they would have to be over twenty one. If court records indicate a guardian was chosen for a child, they would have to be under fourteen, etc.

Hopefully this information will help you if you are in a situation where you need to estimate a time of birth. In subsequent Blogs, we’ll show you how to estimate times of death and marriage. Until then; Happy and Successful Ancestor Hunting!