Calculating the birth date from the age at death is a simple task, but it depends on the data you know.
- If you know only the age in years, you can approximate the birth year.
- If you know the age in years and months, you can expand this information on the date of birth but keep some inaccuracy (the result may be shifted by one month).
- If you know the age in days, you can obtain the most accurate result (applying the proper algorithm).
- Knowing the age in the format years/months/days can give you similarly accurate results, but with some catches.
We are going to deal mainly with the two latter cases.
Calculate the birth date from the death date and the age in days
There are two ways you can do this:
Convert the date of death to Julian day, and subtract the age in days to find the Julian day of the birth date. The inverse conversion, however, is cumbersome and not easy to do by hand.
Separate the age in days into three parts:
- Days in the year of birth;
- Days in the full years;
- Days in the year of death.
And follow the next steps:
- From the date of death, calculate how many days that person lived in the last year. You can approximate the result by multiplying the number of months by 30.4, the average month length.
- Subtract this result from the age in days.
- Find the number of years lived by dividing the last result by 365.25 and rounding down the result.
- Subtracting the number of days in the full years plus the number of days in the last year from the age in days gives us the number of days lived in the first year. We can convert this quantity back to date by dividing it by 30.4 and rounding down the result to find the number of months. You then have to subtract this result from 12 to find the birth month. Subtract the remainder from 30 (or 31, or 28: it depends) to find the birthday.
So many approximations likely cause the result to be slightly off: however, you'd be in the correct month!
Calculate the birth date from the death date with age expressed in years, months, and days
This second way requires you to perform multiple subtractions:
- Subtract the number of days of the age from the one of the death date. Carry over 30.4 if the subtraction gives a negative result.
- Subtract the number of months in the same fashion. Eventually, carry over 12 from the years.
- Subtract the years to find the year of birth.
As for the methods above, we are introducing some small approximations that can make your result inaccurate. The best option, if available, is to use an online calculator with a calendar to calculating this difference for you!
FAQs
If you know the age in the format years/months/days, you can calculate the date of birth from the date of death with three simple subtractions: Subtract the number of days in the age from the death date's days. Subtract the number of months between the two dates. Subtract the years between the two dates.
What is the 8870 method? ›
There is what is called a 30-day-month/or **8870 method which assumes that all months have 30 days, many of the headstones and obituary ages at death appear to have been computed using this method. It's an approximation which agrees with the exact calendar month method about 2/3 of the time.
How to work out how old someone was when they died? ›
Subtract the age from the date of death, using regular decimal subtraction. If the resulting MM and DD are within normal range for month and day, the calculation is done. If the resulting DD came out to either 00 or greater than 30, subtract 70 from it.
How do you format birth and death dates? ›
Some dates with less than three digits will not be recognized. In these cases, use YYYY-MM-DD format for both death and birth dates.
What is your death date called? ›
A death anniversary (or deathday) is the anniversary of the death of a person.
Why is it so hard to accept death? ›
The fear of dying is exacerbated by the horrors that accompany its dreadful outcome. Along with the fear of death is the anger that accompanies the lack of understanding as to why humans must suffer. It may not be death itself but the tragedy of the circ*mstances.
What is the death clock? ›
Welcome to the World Death Clock, a dynamic visualization tool that not only calculates but vividly displays the rate of deaths across different time frames from yearly to per-second intervals.
Can you tell someone's age by their teeth? ›
Scientists estimate age by comparing the stage of tooth formation in the X-rays and bone with known dental growth standards. Figure 1. Human teeth. (Source: Gray's Anatomy)For toddler to age 21, teeth are the most accurate age indicators.
How long should I expect to live? ›
In 2021, the average life expectancy at birth was 79.1 for women and 73.2 for men, according to the Centers for Disease Control and Prevention.
How do you show birth and death date? ›
Birth place and date on the one hand, and death place and date on the other hand, are separated by a long dash.
You can use a statement of death or a death certificate as proof of death. The statement of death is sufficient in most situations to notify the federal government of a death.
What is the date of death unknown? ›
"Date of death unknown" may also be used for people from the more recent past who died in circ*mstances which mean their exact death date is unknown. Historically-recent people whose date of death is likely to have been recorded and could be researched should be included in Category:Date of death missing.
How do I find the date of a deceased person? ›
The Social Security Death Index (SSDI) is a database whose records reveal an individuals' full name and residence at time of application, birth and death dates and last known residence.
How to know the age of death? ›
Teeth and bones. Teeth can tell us how old certain individuals were when they died – especially if they died young.
What will be my age in 2050? ›
If you're wondering, "How old will I be in 2050?": Set your date of birth (you can type in "Mar 4, 2005"). "Calculate age on" should be followed by "Jan 1, 2050" or any other day in 2050, depending on when you want. The age calculator will tell you that on New Year's Day 2050, you'll be 44 years 9 months, 28 days old.
