Add countdown.js.

2 files changed, 1390 insertions, 0 deletions

diff --git a/js/app/counter.js b/js/app/counter.js
new file mode 100644
index 0000000..dad6ec4
--- /dev/null
+++ b/js/app/counter.js
@@ -0,0 +1,24 @@
+(function() {
+	// UTC milliseconds since 1970
+	// Example conversion: date --date 2017-05-16T17:00Z+2 +%s000
+	var SHOWTIME = new Date(1494946800000),
+		DEMO_PAST = 'Last FREE Live Webinar began',
+		DEMO_CURRENT = 'FREE Live Webinar began',
+		DEMO_FUTURE = 'Next FREE Live Webinar begins';
+
+	function update() {
+		var ts = countdown(SHOWTIME, null);
+
+		var counter = document.getElementById('counter'),
+			msg = ts.toHTML('strong', null);
+
+		msg = (ts.value > 0) ?
+			DEMO_PAST+' '+msg+' ago!' :
+			DEMO_FUTURE+' in '+msg+'!';
+
+		counter.innerHTML = msg;
+
+		requestAnimationFrame(update, counter.parentNode);
+	}
+	update();
+})();
diff --git a/js/lib/countdown.js b/js/lib/countdown.js
new file mode 100644
index 0000000..c03a032
--- /dev/null
+++ b/js/lib/countdown.js
@@ -0,0 +1,1366 @@
+/*global window */
+/**
+ * @license countdown.js v2.6.0 http://countdownjs.org
+ * Copyright (c)2006-2014 Stephen M. McKamey.
+ * Licensed under The MIT License.
+ */
+/*jshint bitwise:false */
+
+/**
+ * @public
+ * @type {Object|null}
+ */
+var module;
+
+/**
+ * API entry
+ * @public
+ * @param {function(Object)|Date|number} start the starting date
+ * @param {function(Object)|Date|number} end the ending date
+ * @param {number} units the units to populate
+ * @return {Object|number}
+ */
+var countdown = (
+
+/**
+ * @param {Object} module CommonJS Module
+ */
+function(module) {
+	/*jshint smarttabs:true */
+
+	'use strict';
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MILLISECONDS	= 0x001;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var SECONDS			= 0x002;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MINUTES			= 0x004;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var HOURS			= 0x008;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var DAYS			= 0x010;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var WEEKS			= 0x020;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MONTHS			= 0x040;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var YEARS			= 0x080;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var DECADES			= 0x100;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var CENTURIES		= 0x200;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MILLENNIA		= 0x400;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var DEFAULTS		= YEARS|MONTHS|DAYS|HOURS|MINUTES|SECONDS;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MILLISECONDS_PER_SECOND = 1000;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var SECONDS_PER_MINUTE = 60;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MINUTES_PER_HOUR = 60;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var HOURS_PER_DAY = 24;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MILLISECONDS_PER_DAY = HOURS_PER_DAY * MINUTES_PER_HOUR * SECONDS_PER_MINUTE * MILLISECONDS_PER_SECOND;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var DAYS_PER_WEEK = 7;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var MONTHS_PER_YEAR = 12;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var YEARS_PER_DECADE = 10;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var DECADES_PER_CENTURY = 10;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var CENTURIES_PER_MILLENNIUM = 10;
+
+	/**
+	 * @private
+	 * @param {number} x number
+	 * @return {number}
+	 */
+	var ceil = Math.ceil;
+
+	/**
+	 * @private
+	 * @param {number} x number
+	 * @return {number}
+	 */
+	var floor = Math.floor;
+
+	/**
+	 * @private
+	 * @param {Date} ref reference date
+	 * @param {number} shift number of months to shift
+	 * @return {number} number of days shifted
+	 */
+	function borrowMonths(ref, shift) {
+		var prevTime = ref.getTime();
+
+		// increment month by shift
+		ref.setMonth( ref.getMonth() + shift );
+
+		// this is the trickiest since months vary in length
+		return Math.round( (ref.getTime() - prevTime) / MILLISECONDS_PER_DAY );
+	}
+
+	/**
+	 * @private
+	 * @param {Date} ref reference date
+	 * @return {number} number of days
+	 */
+	function daysPerMonth(ref) {
+		var a = ref.getTime();
+
+		// increment month by 1
+		var b = new Date(a);
+		b.setMonth( ref.getMonth() + 1 );
+
+		// this is the trickiest since months vary in length
+		return Math.round( (b.getTime() - a) / MILLISECONDS_PER_DAY );
+	}
+
+	/**
+	 * @private
+	 * @param {Date} ref reference date
+	 * @return {number} number of days
+	 */
+	function daysPerYear(ref) {
+		var a = ref.getTime();
+
+		// increment year by 1
+		var b = new Date(a);
+		b.setFullYear( ref.getFullYear() + 1 );
+
+		// this is the trickiest since years (periodically) vary in length
+		return Math.round( (b.getTime() - a) / MILLISECONDS_PER_DAY );
+	}
+
+	/**
+	 * Applies the Timespan to the given date.
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @param {Date=} date
+	 * @return {Date}
+	 */
+	function addToDate(ts, date) {
+		date = (date instanceof Date) || ((date !== null) && isFinite(date)) ? new Date(+date) : new Date();
+		if (!ts) {
+			return date;
+		}
+
+		// if there is a value field, use it directly
+		var value = +ts.value || 0;
+		if (value) {
+			date.setTime(date.getTime() + value);
+			return date;
+		}
+
+		value = +ts.milliseconds || 0;
+		if (value) {
+			date.setMilliseconds(date.getMilliseconds() + value);
+		}
+
+		value = +ts.seconds || 0;
+		if (value) {
+			date.setSeconds(date.getSeconds() + value);
+		}
+
+		value = +ts.minutes || 0;
+		if (value) {
+			date.setMinutes(date.getMinutes() + value);
+		}
+
+		value = +ts.hours || 0;
+		if (value) {
+			date.setHours(date.getHours() + value);
+		}
+
+		value = +ts.weeks || 0;
+		if (value) {
+			value *= DAYS_PER_WEEK;
+		}
+
+		value += +ts.days || 0;
+		if (value) {
+			date.setDate(date.getDate() + value);
+		}
+
+		value = +ts.months || 0;
+		if (value) {
+			date.setMonth(date.getMonth() + value);
+		}
+
+		value = +ts.millennia || 0;
+		if (value) {
+			value *= CENTURIES_PER_MILLENNIUM;
+		}
+
+		value += +ts.centuries || 0;
+		if (value) {
+			value *= DECADES_PER_CENTURY;
+		}
+
+		value += +ts.decades || 0;
+		if (value) {
+			value *= YEARS_PER_DECADE;
+		}
+
+		value += +ts.years || 0;
+		if (value) {
+			date.setFullYear(date.getFullYear() + value);
+		}
+
+		return date;
+	}
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_MILLISECONDS	= 0;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_SECONDS		= 1;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_MINUTES		= 2;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_HOURS			= 3;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_DAYS			= 4;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_WEEKS			= 5;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_MONTHS		= 6;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_YEARS			= 7;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_DECADES		= 8;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_CENTURIES		= 9;
+
+	/**
+	 * @private
+	 * @const
+	 * @type {number}
+	 */
+	var LABEL_MILLENNIA		= 10;
+
+	/**
+	 * @private
+	 * @type {Array}
+	 */
+	var LABELS_SINGLUAR;
+
+	/**
+	 * @private
+	 * @type {Array}
+	 */
+	var LABELS_PLURAL;
+
+	/**
+	 * @private
+	 * @type {string}
+	 */
+	var LABEL_LAST;
+
+	/**
+	 * @private
+	 * @type {string}
+	 */
+	var LABEL_DELIM;
+
+	/**
+	 * @private
+	 * @type {string}
+	 */
+	var LABEL_NOW;
+
+	/**
+	 * Formats a number & unit as a string
+	 * 
+	 * @param {number} value
+	 * @param {number} unit
+	 * @return {string}
+	 */
+	var formatter;
+
+	/**
+	 * Formats a number as a string
+	 * 
+	 * @private
+	 * @param {number} value
+	 * @return {string}
+	 */
+	var formatNumber;
+
+	/**
+	 * @private
+	 * @param {number} value
+	 * @param {number} unit unit index into label list
+	 * @return {string}
+	 */
+	function plurality(value, unit) {
+		return formatNumber(value)+((value === 1) ? LABELS_SINGLUAR[unit] : LABELS_PLURAL[unit]);
+	}
+
+	/**
+	 * Formats the entries with singular or plural labels
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @return {Array}
+	 */
+	var formatList;
+
+	/**
+	 * Timespan representation of a duration of time
+	 * 
+	 * @private
+	 * @this {Timespan}
+	 * @constructor
+	 */
+	function Timespan() {}
+
+	/**
+	 * Formats the Timespan as a sentence
+	 * 
+	 * @param {string=} emptyLabel the string to use when no values returned
+	 * @return {string}
+	 */
+	Timespan.prototype.toString = function(emptyLabel) {
+		var label = formatList(this);
+
+		var count = label.length;
+		if (!count) {
+			return emptyLabel ? ''+emptyLabel : LABEL_NOW;
+		}
+		if (count === 1) {
+			return label[0];
+		}
+
+		var last = LABEL_LAST+label.pop();
+		return label.join(LABEL_DELIM)+last;
+	};
+
+	/**
+	 * Formats the Timespan as a sentence in HTML
+	 * 
+	 * @param {string=} tag HTML tag name to wrap each value
+	 * @param {string=} emptyLabel the string to use when no values returned
+	 * @return {string}
+	 */
+	Timespan.prototype.toHTML = function(tag, emptyLabel) {
+		tag = tag || 'span';
+		var label = formatList(this);
+
+		var count = label.length;
+		if (!count) {
+			emptyLabel = emptyLabel || LABEL_NOW;
+			return emptyLabel ? '<'+tag+'>'+emptyLabel+'</'+tag+'>' : emptyLabel;
+		}
+		for (var i=0; i<count; i++) {
+			// wrap each unit in tag
+			label[i] = '<'+tag+'>'+label[i]+'</'+tag+'>';
+		}
+		if (count === 1) {
+			return label[0];
+		}
+
+		var last = LABEL_LAST+label.pop();
+		return label.join(LABEL_DELIM)+last;
+	};
+
+	/**
+	 * Applies the Timespan to the given date
+	 * 
+	 * @param {Date=} date the date to which the timespan is added.
+	 * @return {Date}
+	 */
+	Timespan.prototype.addTo = function(date) {
+		return addToDate(this, date);
+	};
+
+	/**
+	 * Formats the entries as English labels
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @return {Array}
+	 */
+	formatList = function(ts) {
+		var list = [];
+
+		var value = ts.millennia;
+		if (value) {
+			list.push(formatter(value, LABEL_MILLENNIA));
+		}
+
+		value = ts.centuries;
+		if (value) {
+			list.push(formatter(value, LABEL_CENTURIES));
+		}
+
+		value = ts.decades;
+		if (value) {
+			list.push(formatter(value, LABEL_DECADES));
+		}
+
+		value = ts.years;
+		if (value) {
+			list.push(formatter(value, LABEL_YEARS));
+		}
+
+		value = ts.months;
+		if (value) {
+			list.push(formatter(value, LABEL_MONTHS));
+		}
+
+		value = ts.weeks;
+		if (value) {
+			list.push(formatter(value, LABEL_WEEKS));
+		}
+
+		value = ts.days;
+		if (value) {
+			list.push(formatter(value, LABEL_DAYS));
+		}
+
+		value = ts.hours;
+		if (value) {
+			list.push(formatter(value, LABEL_HOURS));
+		}
+
+		value = ts.minutes;
+		if (value) {
+			list.push(formatter(value, LABEL_MINUTES));
+		}
+
+		value = ts.seconds;
+		if (value) {
+			list.push(formatter(value, LABEL_SECONDS));
+		}
+
+		value = ts.milliseconds;
+		if (value) {
+			list.push(formatter(value, LABEL_MILLISECONDS));
+		}
+
+		return list;
+	};
+
+	/**
+	 * Borrow any underflow units, carry any overflow units
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @param {string} toUnit
+	 */
+	function rippleRounded(ts, toUnit) {
+		switch (toUnit) {
+			case 'seconds':
+				if (ts.seconds !== SECONDS_PER_MINUTE || isNaN(ts.minutes)) {
+					return;
+				}
+				// ripple seconds up to minutes
+				ts.minutes++;
+				ts.seconds = 0;
+
+				/* falls through */
+			case 'minutes':
+				if (ts.minutes !== MINUTES_PER_HOUR || isNaN(ts.hours)) {
+					return;
+				}
+				// ripple minutes up to hours
+				ts.hours++;
+				ts.minutes = 0;
+
+				/* falls through */
+			case 'hours':
+				if (ts.hours !== HOURS_PER_DAY || isNaN(ts.days)) {
+					return;
+				}
+				// ripple hours up to days
+				ts.days++;
+				ts.hours = 0;
+
+				/* falls through */
+			case 'days':
+				if (ts.days !== DAYS_PER_WEEK || isNaN(ts.weeks)) {
+					return;
+				}
+				// ripple days up to weeks
+				ts.weeks++;
+				ts.days = 0;
+
+				/* falls through */
+			case 'weeks':
+				if (ts.weeks !== daysPerMonth(ts.refMonth)/DAYS_PER_WEEK || isNaN(ts.months)) {
+					return;
+				}
+				// ripple weeks up to months
+				ts.months++;
+				ts.weeks = 0;
+
+				/* falls through */
+			case 'months':
+				if (ts.months !== MONTHS_PER_YEAR || isNaN(ts.years)) {
+					return;
+				}
+				// ripple months up to years
+				ts.years++;
+				ts.months = 0;
+
+				/* falls through */
+			case 'years':
+				if (ts.years !== YEARS_PER_DECADE || isNaN(ts.decades)) {
+					return;
+				}
+				// ripple years up to decades
+				ts.decades++;
+				ts.years = 0;
+
+				/* falls through */
+			case 'decades':
+				if (ts.decades !== DECADES_PER_CENTURY || isNaN(ts.centuries)) {
+					return;
+				}
+				// ripple decades up to centuries
+				ts.centuries++;
+				ts.decades = 0;
+
+				/* falls through */
+			case 'centuries':
+				if (ts.centuries !== CENTURIES_PER_MILLENNIUM || isNaN(ts.millennia)) {
+					return;
+				}
+				// ripple centuries up to millennia
+				ts.millennia++;
+				ts.centuries = 0;
+				/* falls through */
+			}
+	}
+
+	/**
+	 * Ripple up partial units one place
+	 * 
+	 * @private
+	 * @param {Timespan} ts timespan
+	 * @param {number} frac accumulated fractional value
+	 * @param {string} fromUnit source unit name
+	 * @param {string} toUnit target unit name
+	 * @param {number} conversion multiplier between units
+	 * @param {number} digits max number of decimal digits to output
+	 * @return {number} new fractional value
+	 */
+	function fraction(ts, frac, fromUnit, toUnit, conversion, digits) {
+		if (ts[fromUnit] >= 0) {
+			frac += ts[fromUnit];
+			delete ts[fromUnit];
+		}
+
+		frac /= conversion;
+		if (frac + 1 <= 1) {
+			// drop if below machine epsilon
+			return 0;
+		}
+
+		if (ts[toUnit] >= 0) {
+			// ensure does not have more than specified number of digits
+			ts[toUnit] = +(ts[toUnit] + frac).toFixed(digits);
+			rippleRounded(ts, toUnit);
+			return 0;
+		}
+
+		return frac;
+	}
+
+	/**
+	 * Ripple up partial units to next existing
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @param {number} digits max number of decimal digits to output
+	 */
+	function fractional(ts, digits) {
+		var frac = fraction(ts, 0, 'milliseconds', 'seconds', MILLISECONDS_PER_SECOND, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'seconds', 'minutes', SECONDS_PER_MINUTE, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'minutes', 'hours', MINUTES_PER_HOUR, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'hours', 'days', HOURS_PER_DAY, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'days', 'weeks', DAYS_PER_WEEK, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'weeks', 'months', daysPerMonth(ts.refMonth)/DAYS_PER_WEEK, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'months', 'years', daysPerYear(ts.refMonth)/daysPerMonth(ts.refMonth), digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'years', 'decades', YEARS_PER_DECADE, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'decades', 'centuries', DECADES_PER_CENTURY, digits);
+		if (!frac) { return; }
+
+		frac = fraction(ts, frac, 'centuries', 'millennia', CENTURIES_PER_MILLENNIUM, digits);
+
+		// should never reach this with remaining fractional value
+		if (frac) { throw new Error('Fractional unit overflow'); }
+	}
+
+	/**
+	 * Borrow any underflow units, carry any overflow units
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 */
+	function ripple(ts) {
+		var x;
+
+		if (ts.milliseconds < 0) {
+			// ripple seconds down to milliseconds
+			x = ceil(-ts.milliseconds / MILLISECONDS_PER_SECOND);
+			ts.seconds -= x;
+			ts.milliseconds += x * MILLISECONDS_PER_SECOND;
+
+		} else if (ts.milliseconds >= MILLISECONDS_PER_SECOND) {
+			// ripple milliseconds up to seconds
+			ts.seconds += floor(ts.milliseconds / MILLISECONDS_PER_SECOND);
+			ts.milliseconds %= MILLISECONDS_PER_SECOND;
+		}
+
+		if (ts.seconds < 0) {
+			// ripple minutes down to seconds
+			x = ceil(-ts.seconds / SECONDS_PER_MINUTE);
+			ts.minutes -= x;
+			ts.seconds += x * SECONDS_PER_MINUTE;
+
+		} else if (ts.seconds >= SECONDS_PER_MINUTE) {
+			// ripple seconds up to minutes
+			ts.minutes += floor(ts.seconds / SECONDS_PER_MINUTE);
+			ts.seconds %= SECONDS_PER_MINUTE;
+		}
+
+		if (ts.minutes < 0) {
+			// ripple hours down to minutes
+			x = ceil(-ts.minutes / MINUTES_PER_HOUR);
+			ts.hours -= x;
+			ts.minutes += x * MINUTES_PER_HOUR;
+
+		} else if (ts.minutes >= MINUTES_PER_HOUR) {
+			// ripple minutes up to hours
+			ts.hours += floor(ts.minutes / MINUTES_PER_HOUR);
+			ts.minutes %= MINUTES_PER_HOUR;
+		}
+
+		if (ts.hours < 0) {
+			// ripple days down to hours
+			x = ceil(-ts.hours / HOURS_PER_DAY);
+			ts.days -= x;
+			ts.hours += x * HOURS_PER_DAY;
+
+		} else if (ts.hours >= HOURS_PER_DAY) {
+			// ripple hours up to days
+			ts.days += floor(ts.hours / HOURS_PER_DAY);
+			ts.hours %= HOURS_PER_DAY;
+		}
+
+		while (ts.days < 0) {
+			// NOTE: never actually seen this loop more than once
+
+			// ripple months down to days
+			ts.months--;
+			ts.days += borrowMonths(ts.refMonth, 1);
+		}
+
+		// weeks is always zero here
+
+		if (ts.days >= DAYS_PER_WEEK) {
+			// ripple days up to weeks
+			ts.weeks += floor(ts.days / DAYS_PER_WEEK);
+			ts.days %= DAYS_PER_WEEK;
+		}
+
+		if (ts.months < 0) {
+			// ripple years down to months
+			x = ceil(-ts.months / MONTHS_PER_YEAR);
+			ts.years -= x;
+			ts.months += x * MONTHS_PER_YEAR;
+
+		} else if (ts.months >= MONTHS_PER_YEAR) {
+			// ripple months up to years
+			ts.years += floor(ts.months / MONTHS_PER_YEAR);
+			ts.months %= MONTHS_PER_YEAR;
+		}
+
+		// years is always non-negative here
+		// decades, centuries and millennia are always zero here
+
+		if (ts.years >= YEARS_PER_DECADE) {
+			// ripple years up to decades
+			ts.decades += floor(ts.years / YEARS_PER_DECADE);
+			ts.years %= YEARS_PER_DECADE;
+
+			if (ts.decades >= DECADES_PER_CENTURY) {
+				// ripple decades up to centuries
+				ts.centuries += floor(ts.decades / DECADES_PER_CENTURY);
+				ts.decades %= DECADES_PER_CENTURY;
+
+				if (ts.centuries >= CENTURIES_PER_MILLENNIUM) {
+					// ripple centuries up to millennia
+					ts.millennia += floor(ts.centuries / CENTURIES_PER_MILLENNIUM);
+					ts.centuries %= CENTURIES_PER_MILLENNIUM;
+				}
+			}
+		}
+	}
+
+	/**
+	 * Remove any units not requested
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @param {number} units the units to populate
+	 * @param {number} max number of labels to output
+	 * @param {number} digits max number of decimal digits to output
+	 */
+	function pruneUnits(ts, units, max, digits) {
+		var count = 0;
+
+		// Calc from largest unit to smallest to prevent underflow
+		if (!(units & MILLENNIA) || (count >= max)) {
+			// ripple millennia down to centuries
+			ts.centuries += ts.millennia * CENTURIES_PER_MILLENNIUM;
+			delete ts.millennia;
+
+		} else if (ts.millennia) {
+			count++;
+		}
+
+		if (!(units & CENTURIES) || (count >= max)) {
+			// ripple centuries down to decades
+			ts.decades += ts.centuries * DECADES_PER_CENTURY;
+			delete ts.centuries;
+
+		} else if (ts.centuries) {
+			count++;
+		}
+
+		if (!(units & DECADES) || (count >= max)) {
+			// ripple decades down to years
+			ts.years += ts.decades * YEARS_PER_DECADE;
+			delete ts.decades;
+
+		} else if (ts.decades) {
+			count++;
+		}
+
+		if (!(units & YEARS) || (count >= max)) {
+			// ripple years down to months
+			ts.months += ts.years * MONTHS_PER_YEAR;
+			delete ts.years;
+
+		} else if (ts.years) {
+			count++;
+		}
+
+		if (!(units & MONTHS) || (count >= max)) {
+			// ripple months down to days
+			if (ts.months) {
+				ts.days += borrowMonths(ts.refMonth, ts.months);
+			}
+			delete ts.months;
+
+			if (ts.days >= DAYS_PER_WEEK) {
+				// ripple day overflow back up to weeks
+				ts.weeks += floor(ts.days / DAYS_PER_WEEK);
+				ts.days %= DAYS_PER_WEEK;
+			}
+
+		} else if (ts.months) {
+			count++;
+		}
+
+		if (!(units & WEEKS) || (count >= max)) {
+			// ripple weeks down to days
+			ts.days += ts.weeks * DAYS_PER_WEEK;
+			delete ts.weeks;
+
+		} else if (ts.weeks) {
+			count++;
+		}
+
+		if (!(units & DAYS) || (count >= max)) {
+			//ripple days down to hours
+			ts.hours += ts.days * HOURS_PER_DAY;
+			delete ts.days;
+
+		} else if (ts.days) {
+			count++;
+		}
+
+		if (!(units & HOURS) || (count >= max)) {
+			// ripple hours down to minutes
+			ts.minutes += ts.hours * MINUTES_PER_HOUR;
+			delete ts.hours;
+
+		} else if (ts.hours) {
+			count++;
+		}
+
+		if (!(units & MINUTES) || (count >= max)) {
+			// ripple minutes down to seconds
+			ts.seconds += ts.minutes * SECONDS_PER_MINUTE;
+			delete ts.minutes;
+
+		} else if (ts.minutes) {
+			count++;
+		}
+
+		if (!(units & SECONDS) || (count >= max)) {
+			// ripple seconds down to milliseconds
+			ts.milliseconds += ts.seconds * MILLISECONDS_PER_SECOND;
+			delete ts.seconds;
+
+		} else if (ts.seconds) {
+			count++;
+		}
+
+		// nothing to ripple milliseconds down to
+		// so ripple back up to smallest existing unit as a fractional value
+		if (!(units & MILLISECONDS) || (count >= max)) {
+			fractional(ts, digits);
+		}
+	}
+
+	/**
+	 * Populates the Timespan object
+	 * 
+	 * @private
+	 * @param {Timespan} ts
+	 * @param {?Date} start the starting date
+	 * @param {?Date} end the ending date
+	 * @param {number} units the units to populate
+	 * @param {number} max number of labels to output
+	 * @param {number} digits max number of decimal digits to output
+	 */
+	function populate(ts, start, end, units, max, digits) {
+		var now = new Date();
+
+		ts.start = start = start || now;
+		ts.end = end = end || now;
+		ts.units = units;
+
+		ts.value = end.getTime() - start.getTime();
+		if (ts.value < 0) {
+			// swap if reversed
+			var tmp = end;
+			end = start;
+			start = tmp;
+		}
+
+		// reference month for determining days in month
+		ts.refMonth = new Date(start.getFullYear(), start.getMonth(), 15, 12, 0, 0);
+		try {
+			// reset to initial deltas
+			ts.millennia = 0;
+			ts.centuries = 0;
+			ts.decades = 0;
+			ts.years = end.getFullYear() - start.getFullYear();
+			ts.months = end.getMonth() - start.getMonth();
+			ts.weeks = 0;
+			ts.days = end.getDate() - start.getDate();
+			ts.hours = end.getHours() - start.getHours();
+			ts.minutes = end.getMinutes() - start.getMinutes();
+			ts.seconds = end.getSeconds() - start.getSeconds();
+			ts.milliseconds = end.getMilliseconds() - start.getMilliseconds();
+
+			ripple(ts);
+			pruneUnits(ts, units, max, digits);
+
+		} finally {
+			delete ts.refMonth;
+		}
+
+		return ts;
+	}
+
+	/**
+	 * Determine an appropriate refresh rate based upon units
+	 * 
+	 * @private
+	 * @param {number} units the units to populate
+	 * @return {number} milliseconds to delay
+	 */
+	function getDelay(units) {
+		if (units & MILLISECONDS) {
+			// refresh very quickly
+			return MILLISECONDS_PER_SECOND / 30; //30Hz
+		}
+
+		if (units & SECONDS) {
+			// refresh every second
+			return MILLISECONDS_PER_SECOND; //1Hz
+		}
+
+		if (units & MINUTES) {
+			// refresh every minute
+			return MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE;
+		}
+
+		if (units & HOURS) {
+			// refresh hourly
+			return MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE * MINUTES_PER_HOUR;
+		}
+		
+		if (units & DAYS) {
+			// refresh daily
+			return MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE * MINUTES_PER_HOUR * HOURS_PER_DAY;
+		}
+
+		// refresh the rest weekly
+		return MILLISECONDS_PER_SECOND * SECONDS_PER_MINUTE * MINUTES_PER_HOUR * HOURS_PER_DAY * DAYS_PER_WEEK;
+	}
+
+	/**
+	 * API entry point
+	 * 
+	 * @public
+	 * @param {Date|number|Timespan|null|function(Timespan,number)} start the starting date
+	 * @param {Date|number|Timespan|null|function(Timespan,number)} end the ending date
+	 * @param {number=} units the units to populate
+	 * @param {number=} max number of labels to output
+	 * @param {number=} digits max number of decimal digits to output
+	 * @return {Timespan|number}
+	 */
+	function countdown(start, end, units, max, digits) {
+		var callback;
+
+		// ensure some units or use defaults
+		units = +units || DEFAULTS;
+		// max must be positive
+		max = (max > 0) ? max : NaN;
+		// clamp digits to an integer between [0, 20]
+		digits = (digits > 0) ? (digits < 20) ? Math.round(digits) : 20 : 0;
+
+		// ensure start date
+		var startTS = null;
+		if ('function' === typeof start) {
+			callback = start;
+			start = null;
+
+		} else if (!(start instanceof Date)) {
+			if ((start !== null) && isFinite(start)) {
+				start = new Date(+start);
+			} else {
+				if ('object' === typeof startTS) {
+					startTS = /** @type{Timespan} */(start);
+				}
+				start = null;
+			}
+		}
+
+		// ensure end date
+		var endTS = null;
+		if ('function' === typeof end) {
+			callback = end;
+			end = null;
+
+		} else if (!(end instanceof Date)) {
+			if ((end !== null) && isFinite(end)) {
+				end = new Date(+end);
+			} else {
+				if ('object' === typeof end) {
+					endTS = /** @type{Timespan} */(end);
+				}
+				end = null;
+			}
+		}
+
+		// must wait to interpret timespans until after resolving dates
+		if (startTS) {
+			start = addToDate(startTS, end);
+		}
+		if (endTS) {
+			end = addToDate(endTS, start);
+		}
+
+		if (!start && !end) {
+			// used for unit testing
+			return new Timespan();
+		}
+
+		if (!callback) {
+			return populate(new Timespan(), /** @type{Date} */(start), /** @type{Date} */(end), /** @type{number} */(units), /** @type{number} */(max), /** @type{number} */(digits));
+		}
+
+		// base delay off units
+		var delay = getDelay(units),
+			timerId,
+			fn = function() {
+				callback(
+					populate(new Timespan(), /** @type{Date} */(start), /** @type{Date} */(end), /** @type{number} */(units), /** @type{number} */(max), /** @type{number} */(digits)),
+					timerId
+				);
+			};
+
+		fn();
+		return (timerId = setInterval(fn, delay));
+	}
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.MILLISECONDS = MILLISECONDS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.SECONDS = SECONDS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.MINUTES = MINUTES;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.HOURS = HOURS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.DAYS = DAYS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.WEEKS = WEEKS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.MONTHS = MONTHS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.YEARS = YEARS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.DECADES = DECADES;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.CENTURIES = CENTURIES;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.MILLENNIA = MILLENNIA;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.DEFAULTS = DEFAULTS;
+
+	/**
+	 * @public
+	 * @const
+	 * @type {number}
+	 */
+	countdown.ALL = MILLENNIA|CENTURIES|DECADES|YEARS|MONTHS|WEEKS|DAYS|HOURS|MINUTES|SECONDS|MILLISECONDS;
+
+	/**
+	 * Customize the format settings.
+	 * @public
+	 * @param {Object} format settings object
+	 */
+	var setFormat = countdown.setFormat = function(format) {
+		if (!format) { return; }
+
+		if ('singular' in format || 'plural' in format) {
+			var singular = format.singular || [];
+			if (singular.split) {
+				singular = singular.split('|');
+			}
+			var plural = format.plural || [];
+			if (plural.split) {
+				plural = plural.split('|');
+			}
+
+			for (var i=LABEL_MILLISECONDS; i<=LABEL_MILLENNIA; i++) {
+				// override any specified units
+				LABELS_SINGLUAR[i] = singular[i] || LABELS_SINGLUAR[i];
+				LABELS_PLURAL[i] = plural[i] || LABELS_PLURAL[i];
+			}
+		}
+
+		if ('string' === typeof format.last) {
+			LABEL_LAST = format.last;
+		}
+		if ('string' === typeof format.delim) {
+			LABEL_DELIM = format.delim;
+		}
+		if ('string' === typeof format.empty) {
+			LABEL_NOW = format.empty;
+		}
+		if ('function' === typeof format.formatNumber) {
+			formatNumber = format.formatNumber;
+		}
+		if ('function' === typeof format.formatter) {
+			formatter = format.formatter;
+		}
+	};
+
+	/**
+	 * Revert to the default formatting.
+	 * @public
+	 */
+	var resetFormat = countdown.resetFormat = function() {
+		LABELS_SINGLUAR = ' millisecond| second| minute| hour| day| week| month| year| decade| century| millennium'.split('|');
+		LABELS_PLURAL = ' milliseconds| seconds| minutes| hours| days| weeks| months| years| decades| centuries| millennia'.split('|');
+		LABEL_LAST = ' and ';
+		LABEL_DELIM = ', ';
+		LABEL_NOW = '';
+		formatNumber = function(value) { return value; };
+		formatter = plurality;
+	};
+
+	/**
+	 * Override the unit labels.
+	 * @public
+	 * @param {string|Array=} singular a pipe ('|') delimited list of singular unit name overrides
+	 * @param {string|Array=} plural a pipe ('|') delimited list of plural unit name overrides
+	 * @param {string=} last a delimiter before the last unit (default: ' and ')
+	 * @param {string=} delim a delimiter to use between all other units (default: ', ')
+	 * @param {string=} empty a label to use when all units are zero (default: '')
+	 * @param {function(number):string=} formatNumber a function which formats numbers as a string
+	 * @param {function(number,number):string=} formatter a function which formats a number/unit pair as a string
+	 * @deprecated since version 2.6.0
+	 */
+	countdown.setLabels = function(singular, plural, last, delim, empty, formatNumber, formatter) {
+		setFormat({
+			singular: singular,
+			plural: plural,
+			last: last,
+			delim: delim,
+			empty: empty,
+			formatNumber: formatNumber,
+			formatter: formatter
+		});
+	};
+
+	/**
+	 * Revert to the default unit labels.
+	 * @public
+	 * @deprecated since version 2.6.0
+	 */
+	countdown.resetLabels = resetFormat;
+
+	resetFormat();
+
+	if (module && module.exports) {
+		module.exports = countdown;
+
+	} else if (typeof window.define === 'function' && typeof window.define.amd !== 'undefined') {
+		window.define('countdown', [], function() {
+			return countdown;
+		});
+	}
+
+	return countdown;
+
+})(module);