Date.prototype.set8601 = function (string) {
	var regexp = "([0-9]{4})(-([0-9]{2})(-([0-9]{2})" +
		"(T([0-9]{2}):([0-9]{2})(:([0-9]{2})(\.([0-9]+))?)?" +
		"(Z|(([-+])([0-9]{2}):([0-9]{2})))?)?)?)?";
	var d = string.match(new RegExp(regexp));

	var offset = 0;
	var date = new Date(d[1], 0, 1);

	if (d[3]) { date.setMonth(d[3] - 1); }
	if (d[5]) { date.setDate(d[5]); }
	if (d[7]) { date.setHours(d[7]); }
	if (d[8]) { date.setMinutes(d[8]); }
	if (d[10]) { date.setSeconds(d[10]); }
	if (d[12]) { date.setMilliseconds(Number("0." + d[12]) * 1000); }
	if (d[14]) {
		offset = (Number(d[16]) * 60) + Number(d[17]);
		offset *= ((d[15] == '-') ? 1 : -1);
	}

	offset -= date.getTimezoneOffset();
	var time = (Number(date) + (offset * 60 * 1000));
	this.setTime(Number(time));

	return this;
}

Date.prototype.to8601 = function(){
	function pad(n){return n<10 ? '0'+n : n}
	return this.getUTCFullYear()+'-'
		+ pad(this.getUTCMonth()+1)+'-'
		+ pad(this.getUTCDate())+'T'
		+ pad(this.getUTCHours())+':'
		+ pad(this.getUTCMinutes())+':'
		+ pad(this.getUTCSeconds())+'Z';
}

Date.prototype.getRelative = function(){
	const s = 1000, m = s*60, h = m*60, d = h*24, y = d*365, M = y/12,
	      ref = Date.now(),
	      input = this.getTime(),
	      delta = ref - input,
	      year = Math.round((delta/y)*10)/10,
	      month = Math.round((delta/M)*10)/10,
	      day = Math.round((delta/d)*10)/10,
	      hour = Math.round((delta/h)*10)/10,
	      minute = Math.round((delta/m)*10)/10;

	if (year == 1)
		return "a year ago";
	if (year > 1)
		return Math.round(year)+" years ago";

	if (month == 1)
		return "a month ago";
	if (month > 1)
		return Math.round(month)+" months ago";

	if (day == 1)
		return "yesterday";
	if (day > 1)
		return Math.round(day)+" days ago";

	if (hour == 1)
		return "an hour ago";
	if (hour > 1)
		return Math.round(hour)+" hours ago";

	if (minute == 1)
		return "a minute ago";
	if (minute > 1)
		return Math.round(minute)+" minutes ago";

	return "just now";
};