JavaScript Birthdate Calculator  

 Birthdate Calculator


Month Length: 

Enter date of death and age at death:

Day Month Year
Days Months Years

To perform your calculation, click on this button:

This calculator was made by Ben Buckner
About the Calculator
Calculates birthdate from death date and age of death in year-month-day format. 

All dates, Gregorian or Julian, use New Year on Jan. 1. 

This new version uses two different computation methods: (the 28-day calculation
has some problems and it wasn't very useful, so it has been removed) 

   1.30-day fixed-length months (the "8870" system is a variant of this) 
   2.Calendar-length months 

Please see the explanation of birthdate calculation methods, and keep in mind that 
due to uncertainty as to which calculation method was originally used and due to possible errors in the original calculation, calculated dates should be considered 
to be accurate only to within a few days unless you have good reason to be more confident in them. It is not unusual to encounter original calculation errors as large 
as 1 month, so beware! 

It also now allows Julian calendar dates, but you cannot mix Julian and 
Gregorian dates or ages in the same calculation. Generally, the Julian result 
will be identical, but there are a few exceptions. 

This form uses tables and, of course, the forms interface. If your browser 
does not support these, sorry.