How do I create an age calculator by giving DOB, and it will calculate it in years, months, days, hours, minutes & seconds.

A few simple rules when posting your question.

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To expand upon what I wrote earlier and point 0 of the above list. CodeProject QA section expects you to try google first, to at least try to solve your problem on your own. "Javascript date calculators" returns 4.11 million google results. Many of these will be perfectly suitable for you.

If you feel surprised at my original response, I suggest that you take the time to review a couple dozen questions in the QA section to improve your familiarity with it. Each forum site has it's own 'feel' and set of expectations, this one is no different in that regard.

Getting back to your original question - If you wish to read the documentation for the javascript Date object which you may use for your calculations, you may read it here: W3Schools - js Date object

Finding the difference between two time/dates is as simple as initializing two date objects with the two dates of concern, before subtracting one from another.

Try the following code:

function timeTest()
{
var d1 = new Date();
alert("Press ok to continue. (response time measured)");
var d2 = new Date();
var msDifference = d2.getTime() - d1.getTime();
alert("You took: " + (msDifference / 1000) + " seconds to press ok.");
}