Press the button help again to conceal
help message.
If the date is not normalized meaning
year not 100..3000, month not 01..12
and days are not 1..28/29/30/31 de-
pending on the month, an error mes-
sage in red will be displayed.

Or year not in range:

Example age of person from born and dead dates:

"Total Days" is always positive, the
difference in days between two dates.
Years Months Days is the difference
between date 1 and date 2. It is not a
date in itself, but an interval. it is nor-
malized in that Months are 0..11 and
Days 0..31.
You can use this to figure how many
days you have lived right now. Enter
your birthday as 1. date and the day
today as 2. date press "Show Difference"
and voilá.
"

Press the button help again to conceal
help message.
If the date is not normalized meaning
year not 100..3000, month not 01..12
and days are not 1..28/29/30/31
depending on the month, an error
message in red will be displayed.

Adding years to a date is no problem.
Adding months to a date has problems
when the day for example is 31 in Aug-
ust and the new month is in September
which has 30 days, then the result will
be set to September 30th and not Octo-
ber 1st. Similarly e. g. February.
YMD is not necessarily normalized.
You can add 1000 months for example
or 20000 days if you fancy. See example
how many years and months 10000
days are:

The result being 10000 days are 27 years
5 months and 20 days (depending slightly
on the start date).
Example finding birthdate for Sidsel
Dynesdatter who died 1774.02.07 age
82 years 3 months and 14 days:

She was born October 24th 1691.