very often You will find the statements:
old 78 year, 3 Monath, 2 weeks and 4 days or
old 8 years minus 2 weeks and 5 days
other combination may possible.
It would be very helpfull for my work to have an calulation of the birthday without using other Programs or websites. May your can intergrate such a calulation feature straight to the usefrom entring the death data.
The feature should consider the leap year incl. the settings for the century
I hope You can implement such a feature.