Accurate Human Logical Time Difference Javascript Function

 // Time difference function
	function timeDiff(start, end) {
		//today, now!
		//Get the diff
		var diff = end - start;
		//Create numbers for dividing to get hour, minute and second diff
		var units = [
		1000 * 60 * 60 *24,
		1000 * 60 * 60,
		1000 * 60,
		1000
		];

		var rv = []; // h, m, s array
		//loop through d, h, m, s. we are not gonna use days, its just there to subtract it from the time
		for (var i = 0; i < units.length; ++i) {
			rv.push(Math.floor(diff / units[i]));
			diff = diff % units[i];
		}

		//Get the year of this year
		var thisFullYear = end.getFullYear();
		//Check how many days there where in last month
		var daysInLastMonth = new Date(thisFullYear, end.getMonth(), 0).getDate();
		//Get this month
		var thisMonth = end.getMonth(); 
		//Subtract to get differense between years
		thisFullYear = thisFullYear - start.getFullYear();
		//Subtract to get differense between months
		thisMonth = thisMonth - start.getMonth();
		//If month is less than 0 it means that we are some moths before the start date in the year.
		// So we subtract one year, and add the negative number (month) to 12. (12 + -1 = 11)
		subAddDays = daysInLastMonth - start.getDate();
		thisDay = end.getDate();
		thisMonth = thisMonth - 1;
		if(thisMonth < 0){
			thisFullYear = thisFullYear - 1;
			thisMonth = 12 + thisMonth;
			//Get ends day of the month
		}
		//Subtract the start date from the number of days in the last month, add add the result to todays day of the month
		subAddDays = daysInLastMonth - start.getDate();
		subAddDays = thisDay + subAddDays;

		
		if(subAddDays >= daysInLastMonth){
			subAddDays = subAddDays - daysInLastMonth;
			thisMonth++;
			if (thisMonth > 11){
				thisFullYear++;
				thisMonth = 0;
			}
		}
		return {
			years: thisFullYear,
			months: thisMonth,
			days: subAddDays,
			hours: rv[1],
			minutes: rv[2],
			seconds: rv[3]
		};
	}
	//The start date/From date. Here i add one hour to offset it. 
//	var start = new Date(1814, 3, 20, 1);
	//The end date. today, now!
//	var end = new Date();
	//Get the difference
//	var d = timeDiff(start, end);
	// Log that bitch
//	console.log('years: '+ d.years + '. months: '+ d.months + '. days: ' + d.days + '. hours:' +d.hours+ '. minutes:' + d.minutes + '. seconds: ' + d.seconds);