The rewritten title is: Calculate age based on date of birth in YYYYMMDD format

Question

How to calculate age based on date of birth in YYYYMMDD format? Is it possible to use the Date() function?

I'm looking for a better solution than what I'm using now:

var dob = '19800810';
var year = Number(dob.substr(0, 4));
var month = Number(dob.substr(4, 2)) - 1;
var day = Number(dob.substr(6, 2));
var today = new Date();
var age = today.getFullYear() - year;
if (today.getMonth() < month || (today.getMonth() == month && today.getDate() < day)) {
  age--;
}
alert(age);

Answer 1

try it.

function getAge(dateString) {
    var today = new Date();
    var birthDate = new Date(dateString);
    var age = today.getFullYear() - birthDate.getFullYear();
    var m = today.getMonth() - birthDate.getMonth();
    if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
        age--;
    }
    return age;
}

I believe the only part of your code that looks rough is the substr part.

Fiddle：http://jsfiddle.net/codeandcloud/n33RJ/

Answer 2

I would choose readability:

function _calculateAge(birthday) { // birthday is a date
    var ageDifMs = Date.now() - birthday.getTime();
    var ageDate = new Date(ageDifMs); // miliseconds from epoch
    return Math.abs(ageDate.getUTCFullYear() - 1970);
}

Disclaimer: This method also has accuracy issues, so it cannot be completely trusted. Errors may occur in certain years, certain hours, or daylight saving time (depending on time zone).

If accuracy is very important, I recommend using a library to handle this. Also, @Naveens post is probably the most accurate since it is not time dependent.

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