function isDate(p_Expression){
	return !isNaN(new Date(p_Expression));
}

function dateAdd(p_Interval, p_Number, p_Date){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	if(isNaN(p_Number)){return "invalid number: '" + p_Number + "'";}	

	p_Number = new Number(p_Number);
	var dt = new Date(p_Date);
	switch(p_Interval.toLowerCase()){
		case "yyyy": {// year
			dt.setFullYear(dt.getFullYear() + p_Number);
			break;
		}
		case "q": {		// quarter
			dt.setMonth(dt.getMonth() + (p_Number*3));
			break;
		}
		case "m": {		// month
			dt.setMonth(dt.getMonth() + p_Number);
			break;
		}
		case "y":		// day of year
		case "d":		// day
		case "w": {		// weekday
			dt.setDate(dt.getDate() + p_Number);
			break;
		}
		case "ww": {	// week of year
			dt.setDate(dt.getDate() + (p_Number*7));
			break;
		}
		case "h": {		// hour
			dt.setHours(dt.getHours() + p_Number);
			break;
		}
		case "n": {		// minute
			dt.setMinutes(dt.getMinutes() + p_Number);
			break;
		}
		case "s": {		// second
			dt.setSeconds(dt.getSeconds() + p_Number);
			break;
		}
		case "ms": {		// second
			dt.setMilliseconds(dt.getMilliseconds() + p_Number);
			break;
		}
		default: {
			return "invalid interval: '" + p_Interval + "'";
		}
	}
	return dt;
}

function dateDiff(p_Interval, p_Date1, p_Date2, p_firstdayofweek, p_firstweekofyear){
	if(!isDate(p_Date1)){return "invalid date: '" + p_Date1 + "'";}
	if(!isDate(p_Date2)){return "invalid date: '" + p_Date2 + "'";}
	var dt1 = new Date(p_Date1);
	var dt2 = new Date(p_Date2);

	var iDiffMS = dt2.valueOf() - dt1.valueOf();
	var dtDiff = new Date(iDiffMS);

	var nYears  = dt2.getUTCFullYear() - dt1.getUTCFullYear();
	var nMonths = dt2.getUTCMonth() - dt1.getUTCMonth() + (nYears!=0 ? nYears*12 : 0);
	var nQuarters = parseInt(nMonths/3);
	
	var nMilliseconds = iDiffMS;
	var nSeconds = parseInt(iDiffMS/1000);
	var nMinutes = parseInt(nSeconds/60);
	var nHours = parseInt(nMinutes/60);
	var nDays  = parseInt(nHours/24);
	var nWeeks = parseInt(nDays/7);

	var iDiff = 0;		
	switch(p_Interval.toLowerCase()){
		case "yyyy": return nYears;
		case "q": return nQuarters;
		case "m": return nMonths;
		case "y": 		// day of year
		case "d": return nDays;
		case "w": return nDays;
		case "ww":return nWeeks;
		case "h": return nHours;
		case "n": return nMinutes;
		case "s": return nSeconds;
		case "ms":return nMilliseconds;
		default: return "invalid interval: '" + p_Interval + "'";
	}
}

function datePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}

	var dtPart = new Date(p_Date);
	switch(p_Interval.toLowerCase()){
		case "yyyy": return dtPart.getFullYear();
		case "q": return parseInt(dtPart.getMonth()/3)+1;
		case "m": return dtPart.getMonth()+1;
		case "y": return dateDiff("y", "1/1/" + dtPart.getFullYear(), dtPart);
		case "d": return dtPart.getDate();
		case "w": return dtPart.getDay();
		case "ww":return dateDiff("ww", "1/1/" + dtPart.getFullYear(), dtPart);
		case "h": return dtPart.getHours();
		case "n": return dtPart.getMinutes();
		case "s": return dtPart.getSeconds();
		case "ms":return dtPart.getMilliseconds();
		default: return "invalid interval: '" + p_Interval + "'";
	}
}

function weekdayName(p_Date, p_abbreviate){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	var dt = new Date(p_Date);
	var retVal = dt.toString().split(' ')[0];
	var retVal = Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday')[dt.getDay()];
	if(p_abbreviate==true){retVal = retVal.substring(0, 3)}	// abbr to 1st 3 chars
	return retVal;
}

function monthName(p_Date, p_abbreviate){
	if(!isDate(p_Date)){return "invalid date: '" + p_Date + "'";}
	var dt = new Date(p_Date);	
	var retVal = Array('January','February','March','April','May','June','July','August','September','October','November','December')[dt.getMonth()];
	if(p_abbreviate==true){retVal = retVal.substring(0, 3)}	// abbr to 1st 3 chars
	return retVal;
}

function IsDate(p_Expression){
	return isDate(p_Expression);
}
function DateAdd(p_Interval, p_Number, p_Date){
	return dateAdd(p_Interval, p_Number, p_Date);
}
function DateDiff(p_interval, p_date1, p_date2, p_firstdayofweek, p_firstweekofyear){
	return dateDiff(p_interval, p_date1, p_date2, p_firstdayofweek, p_firstweekofyear);
}
function DatePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear){
	return datePart(p_Interval, p_Date, p_firstdayofweek, p_firstweekofyear);
}
function WeekdayName(p_Date){
	return weekdayName(p_Date);
}
function MonthName(p_Date){
	return monthName(p_Date);
}

function parseDateString(sDate) {
 // by EW, to correct Safari date problems
 	var s = sDate;
	var s_array = s.split(' ');
	var d_array = s_array[0].split('/');
	var t_array = s_array[1].split(':');
	if (t_array[0] == "12") { t_array[0] = "0"; } 
	if (s_array[2] == "PM") { t_array[0] = parseInt(t_array[0]) + 12; }
	var oDate = new Date(d_array[2], (d_array[0] - 1), d_array[1], t_array[0], t_array[1], t_array[2], 0);
	return(oDate);
}

/*
	Date Format 1.1
	(c) 2007 Steven Levithan <stevenlevithan.com>
	MIT license
	With code by Scott Trenda (Z and o flags, and enhanced brevity)
*/

/*** dateFormat
	Accepts a date, a mask, or a date and a mask.
	Returns a formatted version of the given date.
	The date defaults to the current date/time.
	The mask defaults ``"ddd mmm d yyyy HH:MM:ss"``.
*/
var dateFormat = function () {
	var	token        = /d{1,4}|m{1,4}|yy(?:yy)?|([HhMsTt])\1?|[LloZ]|"[^"]*"|'[^']*'/g,
		timezone     = /\b(?:[PMCEA][SDP]T|(?:Pacific|Mountain|Central|Eastern|Atlantic) (?:Standard|Daylight|Prevailing) Time|(?:GMT|UTC)(?:[-+]\d{4})?)\b/g,
		timezoneClip = /[^-+\dA-Z]/g,
		pad = function (value, length) {
			value = String(value);
			length = parseInt(length) || 2;
			while (value.length < length)
				value = "0" + value;
			return value;
		};

	// Regexes and supporting functions are cached through closure
	return function (date, mask) {
		// Treat the first argument as a mask if it doesn't contain any numbers
		if (
			arguments.length == 1 &&
			(typeof date == "string" || date instanceof String) &&
			!/\d/.test(date)
		) {
			mask = date;
			date = undefined;
		}

		date = date ? new Date(date) : new Date();
		if (isNaN(date))
			throw "invalid date";

		var dF = dateFormat;
		mask   = String(dF.masks[mask] || mask || dF.masks["default"]);

		var	d = date.getDate(),
			D = date.getDay(),
			m = date.getMonth(),
			y = date.getFullYear(),
			H = date.getHours(),
			M = date.getMinutes(),
			s = date.getSeconds(),
			L = date.getMilliseconds(),
			o = date.getTimezoneOffset(),
			flags = {
				d:    d,
				dd:   pad(d),
				ddd:  dF.i18n.dayNames[D],
				dddd: dF.i18n.dayNames[D + 7],
				m:    m + 1,
				mm:   pad(m + 1),
				mmm:  dF.i18n.monthNames[m],
				mmmm: dF.i18n.monthNames[m + 12],
				yy:   String(y).slice(2),
				yyyy: y,
				h:    H % 12 || 12,
				hh:   pad(H % 12 || 12),
				H:    H,
				HH:   pad(H),
				M:    M,
				MM:   pad(M),
				s:    s,
				ss:   pad(s),
				l:    pad(L, 3),
				L:    pad(L > 99 ? Math.round(L / 10) : L),
				t:    H < 12 ? "a"  : "p",
				tt:   H < 12 ? "am" : "pm",
				T:    H < 12 ? "A"  : "P",
				TT:   H < 12 ? "AM" : "PM",
				Z:    (String(date).match(timezone) || [""]).pop().replace(timezoneClip, ""),
				o:    (o > 0 ? "-" : "+") + pad(Math.floor(Math.abs(o) / 60) * 100 + Math.abs(o) % 60, 4)
			};

		return mask.replace(token, function ($0) {
			return ($0 in flags) ? flags[$0] : $0.slice(1, $0.length - 1);
		});
	};
}();

// Some common format strings
dateFormat.masks = {
	"default":       "ddd mmm d yyyy HH:MM:ss",
	shortDate:       "m/d/yy",
	mediumDate:      "mmm d, yyyy",
	longDate:        "mmmm d, yyyy",
	fullDate:        "dddd, mmmm d, yyyy",
	shortTime:       "h:MM TT",
	mediumTime:      "h:MM:ss TT",
	longTime:        "h:MM:ss TT Z",
	isoDate:         "yyyy-mm-dd",
	isoTime:         "HH:MM:ss",
	isoDateTime:     "yyyy-mm-dd'T'HH:MM:ss",
	isoFullDateTime: "yyyy-mm-dd'T'HH:MM:ss.lo"
};

// Internationalization strings
dateFormat.i18n = {
	dayNames: [
		"Sun", "Mon", "Tue", "Wed", "Thr", "Fri", "Sat",
		"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"
	],
	monthNames: [
		"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
		"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"
	]
};

// For convenience...
Date.prototype.format = function (mask) {
	return dateFormat(this, mask);
}