How to calculate user Age based on 2 date fields using a Scope App?

[cms1]

I have two date fields on a scoped app, those are: u_received_date , u_dob

Subtracting these values will tell me the age of the user at the time the request was received. 

I have created the following Business Rule but it doesn't calculate the age correctly.

For example, 

If the received date = 07/10/18 and the date of birth = 08/18/1979 the value being populated is 39 and it should be 38. Please see my code below any help will be appreciated.

(function executeRule(current, previous /*null when async*/) {
var recDa = new GlideDateTime(current.u_received_date.getDisplayValue());
var recDaYear = recDa.getYearLocalTime();

var bday = new GlideDateTime(current.u_dob.getDisplayValue());
bdayYear = bday.getYearLocalTime();
var age = recDaYear - bdayYear;

//gs.addInfoMessage(age);
current.u_age = age;
})(current, previous);

[cms1]

Unfortunately I can not use dateDiff in a scoped app 😞

[cms1]

Thank you everyone - I was able to get the following to work using Scoped app: 

(function executeRule(current, previous /*null when async*/) {

var gdt1 = new GlideDateTime(current.u_received_date.getDisplayValue());
var gdt2 = new GlideDateTime(current.u_dob.getDisplayValue());

duration = GlideDateTime.subtract( gdt2, gdt1 ).getDayPart();
duration = parseInt( duration / 365 ); // Years

//gs.addInfoMessage(duration);
current.u_age = duration;

})(current, previous);

[Daniele Songini · Accepted solution]

Hi,

Please mark this as "Correct Answer" if I have given you a sufficient answer and you have no other questions.

Best Regards,
Daniele

[cms1]

FYI - I also did the following: 

current.u_age = duration.toPrecision(2);  //added to avoid the decimal point