Dear Cheryl: Beware the 8870 system for figuring the date of birth from age at death. It only works about a third of the time. The recommendation is that you NOT use calculated dates in your data. At best, such dates can only be considered as a guess. The main reason for this is that there are - were - a number of different ways used by undertakers/tombstone carvers and newspaper editors to calculate how old a person was at death. The two most prominent methods were the "actual method" - which took into consideration the actual number of days in each month in determining the number of days old a person was at death - and the "30-day method" - which assumed that all months have 30 days no matter what. The 8870 method only works if the "all months have 30 days" method was used to calculate the age at death (or the number of days old was fewer than the day of the month of death - in which case it's easier to just do the math for the days, month and years).This 30-day method was actually taught in school in the latter half of the 19th century. There were other elaborate systems used to calculate ages, almost too complicated to explain (and I've forgotten them anyway <g>). In the late 1980s and early 1990s I did a survey of several hundred instances where the actual birth date was known from other sources and I used the two above-mentioned methods to calculate the birth date from age at death found on a tombstone or in an obituary. The result was that the person who did the age calculations used the "actual days method" about a third of the time and also used the "30-day method" about a third of the time. In the rest of the cases neither of these two methods of date calculation worked, indicating an error was made in the original calculation or some other method was used. (Note that in the case where the month preceding death had 30 days, either method would work.) For the above reasons, calculated birth dates are frowned upon. Their best legitimate use is for trying to determine if a "John Smith" whose age and death date are on his stone in the town cemetery is the same "John Smith" shown in the town birth records as being born on a given date (and thus providing documentation as to the names of his parents). When I encounter a date of death and age at death but nor birth date, I enter the year of birth only, the exact date of death and then footnote the age at death. Sadly, a great number of calculated dates posted on the Internet without noting that the date is calculated. Even though it can be shown that any calculated birth date has two chances out three of being wrong, others accept these dates as "fact." Richard ----- Original Message ----- From: "Cheryl Rothwell" <historysleuth@gmail.com> To: "ILLOGAN" <illogan@rootsweb.com> Sent: Tuesday, August 21, 2007 3:25 PM Subject: [ILLOGAN] birth date calculator > Put your math skills to work! [courtesy Morgan Johnson] > > HOW TO FIGURE A BIRTHDATE > > REMEMBER THIS NUMBER: 8870 > > This is not an error: It is the number to remember when you want to find > the > birthdate of someone when you only have the date of death and age. > > How do you figure the birthdate? > > Suppose the person died May 6, 1889, at the age of > 71 years, 7 months, 9 days. > > 1. Write the year, month, day as: ----------- 18890506 > 2. Subtract the age at death: ---------------- 710709 > 3. This gives the figure: ------------------------ 18179797 > 4. Now subtract 8870: -------------------------- 8870 > 5. The result is: ----------------------------------- 18170927 > > Year 1817, 9th month (Sept), 27th day or 27 Sept, 1817 > > I don't know if it is accurate or not. > > The easier but not necessarily more accurate way: > http://longislandgenealogy.com/birth.html or > http://www.progenealogists.com/birthfromdeath.htm > ________ > Logan County ILGenWeb: http://www.rootsweb.com/~illogan > > To unsubscribe send a message to: > ILLOGAN-request@Rootsweb.com > with unsubscribe as the subject. > > > ------------------------------- > To unsubscribe from the list, please send an email to > ILLOGAN-request@rootsweb.com with the word 'unsubscribe' without the > quotes in the subject and the body of the message

Richard - enlightening information. Thanks for sharing. Bill Stephenson ----- Original Message ----- From: "Richard A. Pence" <richardpence@pipeline.com> To: <illogan@rootsweb.com> Sent: Tuesday, August 21, 2007 4:02 PM Subject: Re: [ILLOGAN] birth date calculator | Dear Cheryl: | | Beware the 8870 system for figuring the date of birth from age at death. It | only works about a third of the time. The recommendation is that you NOT use | calculated dates in your data. At best, such dates can only be considered as | a guess. | | The main reason for this is that there are - were - a number of different | ways used by undertakers/tombstone carvers and newspaper editors to | calculate how old a person was at death. The two most prominent methods were | the "actual method" - which took into consideration the actual number of | days in each month in determining the number of days old a person was at | death - and the "30-day method" - which assumed that all months have 30 days | no matter what. The 8870 method only works if the "all months have 30 days" | method was used to calculate the age at death (or the number of days old was | fewer than the day of the month of death - in which case it's easier to just | do the math for the days, month and years).This 30-day method was actually | taught in school in the latter half of the 19th century. | | There were other elaborate systems used to calculate ages, almost too | complicated to explain (and I've forgotten them anyway <g>). | | In the late 1980s and early 1990s I did a survey of several hundred | instances where the actual birth date was known from other sources and I | used the two above-mentioned methods to calculate the birth date from age | at death found on a tombstone or in an obituary. The result was that the | person who did the age calculations used the "actual days method" about a | third of the time and also used the "30-day method" about a third of the | time. In the rest of the cases neither of these two methods of date | calculation worked, indicating an error was made in the original calculation | or some other method was used. (Note that in the case where the month | preceding death had 30 days, either method would work.) | | For the above reasons, calculated birth dates are frowned upon. Their best | legitimate use is for trying to determine if a "John Smith" whose age and | death date are on his stone in the town cemetery is the same "John Smith" | shown in the town birth records as being born on a given date (and thus | providing documentation as to the names of his parents). | | When I encounter a date of death and age at death but nor birth date, I | enter the year of birth only, the exact date of death and then footnote the | age at death. | | Sadly, a great number of calculated dates posted on the Internet without | noting that the date is calculated. Even though it can be shown that any | calculated birth date has two chances out three of being wrong, others | accept these dates as "fact." | | Richard | | | ----- Original Message ----- | From: "Cheryl Rothwell" <historysleuth@gmail.com> | To: "ILLOGAN" <illogan@rootsweb.com> | Sent: Tuesday, August 21, 2007 3:25 PM | Subject: [ILLOGAN] birth date calculator | | | > Put your math skills to work! [courtesy Morgan Johnson] | > | > HOW TO FIGURE A BIRTHDATE | > | > REMEMBER THIS NUMBER: 8870 | > | > This is not an error: It is the number to remember when you want to find | > the | > birthdate of someone when you only have the date of death and age. | > | > How do you figure the birthdate? | > | > Suppose the person died May 6, 1889, at the age of | > 71 years, 7 months, 9 days. | > | > 1. Write the year, month, day as: ----------- 18890506 | > 2. Subtract the age at death: ---------------- 710709 | > 3. This gives the figure: ------------------------ 18179797 | > 4. Now subtract 8870: -------------------------- 8870 | > 5. The result is: ----------------------------------- 18170927 | > | > Year 1817, 9th month (Sept), 27th day or 27 Sept, 1817 | > | > I don't know if it is accurate or not. | > | > The easier but not necessarily more accurate way: | > http://longislandgenealogy.com/birth.html or | > http://www.progenealogists.com/birthfromdeath.htm | > ________ | > Logan County ILGenWeb: http://www.rootsweb.com/~illogan | > | > To unsubscribe send a message to: | > ILLOGAN-request@Rootsweb.com | > with unsubscribe as the subject. | > | > | > ------------------------------- | > To unsubscribe from the list, please send an email to | > ILLOGAN-request@rootsweb.com with the word 'unsubscribe' without the | > quotes in the subject and the body of the message | | ________ | Logan County ILGenWeb: http://www.rootsweb.com/~illogan | | To unsubscribe send a message to: | ILLOGAN-request@Rootsweb.com | with unsubscribe as the subject. | | | ------------------------------- | To unsubscribe from the list, please send an email to ILLOGAN-request@rootsweb.com with the word 'unsubscribe' without the quotes in the subject and the body of the message | |