Moment.js - how do I get the number of years since a date, not rounded up?

There appears to be a difference function that accepts time intervals to use as well as an option to not round the result. So, something like

Math.floor(moment(new Date()).diff(moment("02/26/1978","MM/DD/YYYY"),'years',true)))

I haven't tried this, and I'm not completely familiar with moment, but it seems like this should get what you want (without having to reset the month).

http://jsfiddle.net/xR8t5/27/

if you do not want fraction values:

var years = moment().diff('1981-01-01', 'years',false);
alert( years);

if you want fraction values:

var years = moment().diff('1981-01-01', 'years',true);
alert( years);

Units can be [seconds, minutes, hours, days, weeks, months, years]

Using moment.js is as easy as:

var years = moment().diff('1981-01-01', 'years');
var days = moment().diff('1981-01-01', 'days');

For additional reference, you can read moment.js official documentation.