Difference between two Date objects

diffcalendar.js

var diff 
	,I = new Date('2016-01-01T00:00:02')
	,O = new Date('2017-01-01T00:00:01')
;


/**
 * Calendar difference between two dates
 *
 * It takes into account the number of days in a month,
 * leap years, seconds and timezones.
 *
 * @author Sergei Sokolov
 * Moscow, July 19, 2016
 */
diff = {
	years   : 0
	,months : 0
	,days   : 0
	,hours  : 0
	,minutes: 0
	,seconds: 0
};

diff.seconds += O.getSeconds() - I.getSeconds();
if( diff.seconds < 0) {
	diff.seconds += 60;
	diff.minutes--;
}

diff.minutes += O.getMinutes() - I.getMinutes();
if( diff.minutes < 0) {
	diff.minutes += 60;
	diff.hours--;
}

diff.hours += O.getHours() - I.getHours();
if( diff.hours < 0) {
	diff.hours += 24;
	diff.days--;
}

diff.days += O.getDate() - I.getDate();
if( diff.days < 0) {
	diff.days += new Date( O.getFullYear(), O.getMonth(), 0).getDate();
	diff.months--;
}

diff.months += O.getMonth() - I.getMonth();
if( diff.months < 0) {
	diff.months += 12;
	diff.years--;
}

diff.years += O.getFullYear() - I.getFullYear();