Calculate age based on date of birth for dd/mm/yyyy date format

Question

I want to calculate the age based on the date of birth. I can do it easily for date format mm/dd/yyyy but when I try to do the same for dd/mm/yyyy I got age = NaN. Here is my code logic:

$('#DateOfBirth').datepicker({
        onSelect: function (value, ui) {
            var today = new Date(),
                dob = new Date(value),

                age = today.getFullYear() - dob.getFullYear(); //This is the update
            $('#age').val(age);
            alert(age);
        },
        //maxDate: "-16Y",
        maxDate: maxDateVal,
        showOn: "both",
        buttonImage: "",
        dateFormat: "dd/mm/yy",
        changeMonth: true,
        changeYear: true,
        yearRange: '1920:c'

    }).keydown(function (e) {
        if (e.keyCode == 8 || e.keyCode == 46) {
            $(e.target).val("");
        } else {
            e.preventDefault();
            return false;
        }
    });

do you want age in years only or in terms for years,months,day — , Oct 17 '15 at 18:07
@C0smo thanks sir for your comment. ... I want it in years please — Ibrahim Amer, Oct 17 '15 at 18:08
I solved the same problem, on the first day of javascript. it's not a typical problem. just use split() function to extract the year from the input date and subtract from the current year. for split() function definition search google. — Sandipan Guha, Oct 17 '15 at 18:36

score 5 · Accepted Answer · edited May 23 '17 at 12:33

The reason this happens is because new Date(ValueHere) calls Date.parse() which requires a valid format. See below for reference to specifics.

A solution for you, with Regex.

Instead Of:

dob = new Date(value),

Use: (Edited for your particular format)

dob = new Date(value.replace(/(\d{2})[-/](\d{2})[-/](\d+)/, "$2/$1/$3"));

A trimmed down fiddle to demonstrate solution: (updated for your particular format)

http://jsfiddle.net/chrislewispac/e7zjskos/2/

from: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date

and: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse

new Date(dateString);

dateString:

String value representing a date. The string should be in a format recognized by the Date.parse() method (IETF-compliant RFC 2822 timestamps and also a version of ISO8601).

Invalid values in date strings not recognized as ISO format as defined by ECMA-262 may or may not result in NaN, depending on the browser and values provided.

Link to ECMA-262 date standards:

http://www.ecma-international.org/ecma-262/6.0/index.html#sec-date-time-string-format

And link to StackOverflow solutions:

Convert dd-mm-yyyy string to date

Thanks sir for your answer ... I tried your approach but I got an invalid date for dob — Ibrahim Amer, Oct 17 '15 at 18:29
My apologies, try new code. I had to adjust the regex for your specific format. — Chris L, Oct 17 '15 at 18:34
Thank you sir for your answer and commitment this was the solution for me :))) ... I had another issue raised but not related to UI ... thank you sir anyway — Ibrahim Amer, Oct 17 '15 at 18:47

Sandipan Guha · Answer 2 · 2015-10-17T19:18:49.330

found it! this is the complete code of mine:

<head>
<title>Know your age</title>
</head>

<body>
<div>

<h3>Enter your Birth Date</h3> </div>
<div><input type="date" id="birthdate" /> <input type="button" value="Submit" id="acceptbutton" /> </div>
</body>
<script>
function getAge(){
var newDateObject = new Date();

var newObjectCurrentYear = newDateObject.getFullYear();

var userDateObject = document.getElementById("birthdate").value;

var userDateObjectPieces = userDateObject.split("-");

var userObjectYear = userDateObjectPieces[0];

if ( newObjectCurrentYear > userObjectYear){
var currentAge = parseInt(newObjectCurrentYear) - parseInt(userObjectYear);
alert("Your Current Age is: " + currentAge + " " +(currentAge>1?"years":"year"));
}

else{
alert("Birth-Year must be lower than Current-Year.\nPlease Enter Again.");
}

}

var simpleButton = document.getElementById("acceptbutton");
simpleButton.addEventListener("click",getAge);
</script>
</html>

This will give you your current age in alert box.

P.S. point to say, 'date' input not supported in all browsers!Works properly on Chrome!

Calculate age based on date of birth for dd/mm/yyyy date format

2 Answers2