Acrobat Javascript help

Hello,

I'm trying to create a form wich include couple variable like age, date of birth and gender.

We use a id number made of 4 letters ans 8 digits, made of:

3 first letter of last name 1st letter of first name;

Digits represent YY MM* DD and 2 administrative numbers

example John Doe born janurary 20th of 1988  would be DOEJ 8801 2013

* female see month added of 50, eg; Janurary = 51 until december = 62

Example Sarah Andrews born october 13th of 1990 would be ANDS 9061 1312

I was able to calculate a script wich generale a date of birth only for male and i tried verry hard to do it with females too but I'm not enough confortable with scripting. 

I'm also unsure how to deal with the years of Y2K but I could deal with it after 😅 (i guess it's in the 2 last digits, but cannot see any difference in numbers of 19' and 20' folks..)

Thanks a lot.

PS: using Acrobat Pro 2017 on MacOs