get the duration between 2 dates and return a json with 3 values, years, months and days. like you want to obtain duration between 10/02/2013 to 25/05/2014 the function will return {years:1 months:3 days:15}

duration.js

function duration(since, until) {

	//if first date is greater that the first, we fix the order
	if (since > until) {
		var temp = since;
		since = until;
		until = temp;
	}

	var years,months,days;
	
	//Years
	years = (until.getFullYear() - since.getFullYear());
	if (until.getMonth() == since.getMonth()){
		if (since.getDate() < (until.getDate()-1)) {
			years += 1;
		}
		if(since.getDate()==until.getDate()){
				years+= 1;
		}
	}
	if(since.getMonth() > until.getMonth()){
			years = (years - 1);
	}
	//Months
	if(since.getDate() > until.getDate()){
		if(since.getMonth() > (until.getMonth()-1)){
			months = 11 - (since.getMonth() - until.getMonth());
			if (since.getMonth() == until.getMonth()){
				months = 11;
			}
		}else{
			months = until.getMonth() - since.getMonth() - 1;
		}
	}else{
		if(since.getMonth() > until.getMonth()){
			months = 12 - (until.getMonth() - since.getMonth());
		}else{
			months = until.getMonth() - since.getMonth();
		}
	}
	//Days
	if(since.getDate() > (until.getDate()-1)){
		var days_pm = dayssInmonths(until.getMonth(until.getMonth()-1));
		days =  days_pm - since.getDate() + until.getDate();
		if((since.getMonth() == until.getMonth()) & (since.getDate()==until.getDate())){			
			days = 0;
		}
	}else{
		days = until.getDate() - since.getDate();
	}
	
	return ({"years":years,"months":months,"days":days});
}

function dayssInmonths(date){
	date = new Date(date);
	return 32 - new Date(date.getFullYear(), date.getMonth(), 32).getDate();
}

I'm gonna try...

it gets me NaN for years months and days ... whats wrong?