How can I calculate the number of years between two dates?

Solution 1:

Sleek foundation javascript function.

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

Solution 2:

Probably not the answer you're looking for, but at 2.6kb, I would not try to reinvent the wheel and I'd use something like moment.js. Does not have any dependencies.

The diff method is probably what you want: http://momentjs.com/docs/#/displaying/difference/

Solution 3:

Using pure javascript Date(), we can calculate the numbers of years like below

document.getElementById('getYearsBtn').addEventListener('click', function () {
  var enteredDate = document.getElementById('sampleDate').value;
  // Below one is the single line logic to calculate the no. of years...
  var years = new Date(new Date() - new Date(enteredDate)).getFullYear() - 1970;
  console.log(years);
});

<input type="text" id="sampleDate" value="1980/01/01">
<div>Format: yyyy-mm-dd or yyyy/mm/dd</div><br>
<button id="getYearsBtn">Calculate Years</button>

Solution 4:

No for-each loop, no extra jQuery plugin needed... Just call the below function.. Got from Difference between two dates in years

        function dateDiffInYears(dateold, datenew) {
            var ynew = datenew.getFullYear();
            var mnew = datenew.getMonth();
            var dnew = datenew.getDate();
            var yold = dateold.getFullYear();
            var mold = dateold.getMonth();
            var dold = dateold.getDate();
            var diff = ynew - yold;
            if (mold > mnew) diff--;
            else {
                if (mold == mnew) {
                    if (dold > dnew) diff--;
                }
            }
            return diff;
        }