datestime.js

/**
 * Get how much time has passed since refdate to date.
 * @param date
 * @param refdate
 * @returns Json representing the time passed in with years, months and days.
 * E.g. From 15.03.1994 to 24.05.2016 the time passed is
 * 22years, 2 months and 9 days.
 */
function timePassed(date, refdate) {
	var year = date.getFullYear();
	var refYear = refdate.getFullYear();
	var month = date.getMonth();
	var refMonth = refdate.getMonth();
	var day = date.getDate();
	var refDay = refdate.getDate();
	
	//Calculate how many years have passed;
	var years = refYear - year;
	if(month > refMonth) {
		years --;
	} else if (month == refMonth) {
		if(day > refDay) {
			years --;
		}
	}
	
	//Calculate how many months since last year turned
	var months = 0;// = 12 - month - refMonth;
	if(month < refMonth) {
		months = refMonth - month;
		if(day > refDay) {
			months = months - 1;
		}
	} else {
		if(month > refMonth) {
			months = refMonth;
			months = months + 11 - month;
			if(day < refDay) {
				months = months - 1;
			}
		} else {
			if(day > refDay) {
				months = 11;
			}
		}
	}
		
	//Calculate how many days since last month turned.
	var days;
	if(day == refDay) {
		days = 0;
	} else {
		days = daysInMonth(refMonth, refYear) - day + 1;
	}
    var passed = new Object();
    passed.years = years;
    passed.months = months;
    passed.days = days;

    return passed;
}

//Get number of days in a specific month of a specific year.
function daysInMonth(month,year) {
    return new Date(year, month, 0).getDate();
}

/**
 * Compares two date jsons.
 * @param date1 First date.
 * @param date2 Second date.
 * @returns 1 if date1 is bigger (older) than date2;
 *          0 if the two ages are equal;
 *         -1 if date1 is smaller (younger) than date2;
 */
function compareDates(date1, date2) {
	if(date1.years > date2.years) {
		return 1;
	} else {
		if(date1.years < date2.years) {
			return  -1;
		} else {//years are equal, compare months.
			if(date1.monghts > date2.months) {
				return 1;
			} else {
				if(date1.monghts < date2.months) {
					return -1;
				} else {//months are equal, compare days.
					if(date1.days > date2.days) {
						return 1;
					} else {
						if(date1.days < date2.days) {
							return -1;
						} else {//years, months and days are all equal.
							return 0;
						}
					}
				}
			}
		}
	}
}