// ===================================================================
// Author: Matt Kruse <matt@mattkruse.com>
// WWW: http://www.mattkruse.com/
//
// NOTICE: You may use this code for any purpose, commercial or
// private, without any further permission from the author. You may
// remove this notice from your final code if you wish, however it is
// appreciated by the author if at least my web site address is kept.
//
// You may *NOT* re-distribute this code in any way except through its
// use. That means, you can include it in your product, or your web
// site, or any other form where the code is actually being used. You
// may not put the plain javascript up on your site for download or
// include it in your javascript libraries for download. 
// If you wish to share this code with others, please just point them
// to the URL instead.
// Please DO NOT link directly to my .js files from your site. Copy
// the files to your server and use them there. Thank you.
// ===================================================================

// HISTORY
// ------------------------------------------------------------------
// May 17, 2003: Fixed bug in parseDate() for dates <1970
// March 11, 2003: Added parseDate() function
// March 11, 2003: Added "NNN" formatting option. Doesn't match up
//                 perfectly with SimpleDateFormat formats, but 
//                 backwards-compatability was required.

// ------------------------------------------------------------------
// These functions use the same 'format' strings as the 
// java.text.SimpleDateFormat class, with minor exceptions.
// The format string consists of the following abbreviations:
// 
// Field        | Full Form          | Short Form
// -------------+--------------------+-----------------------
// Year         | yyyy (4 digits)    | yy (2 digits), y (2 or 4 digits)
// Month        | MMM (name or abbr.)| MM (2 digits), M (1 or 2 digits)
//              | NNN (abbr.)        |
// Day of Month | dd (2 digits)      | d (1 or 2 digits)
// Day of Week  | EE (name)          | E (abbr)
// Hour (1-12)  | hh (2 digits)      | h (1 or 2 digits)
// Hour (0-23)  | HH (2 digits)      | H (1 or 2 digits)
// Hour (0-11)  | KK (2 digits)      | K (1 or 2 digits)
// Hour (1-24)  | kk (2 digits)      | k (1 or 2 digits)
// Minute       | mm (2 digits)      | m (1 or 2 digits)
// Second       | ss (2 digits)      | s (1 or 2 digits)
// AM/PM        | a                  |
//
// NOTE THE DIFFERENCE BETWEEN MM and mm! Month=MM, not mm!
// Examples:
//  "MMM d, y" matches: January 01, 2000
//                      Dec 1, 1900
//                      Nov 20, 00
//  "M/d/yy"   matches: 01/20/00
//                      9/2/00
//  "MMM dd, yyyy hh:mm:ssa" matches: "January 01, 2000 12:30:45AM"
// ------------------------------------------------------------------

var MONTH_NAMES=new Array('January','February','March','April','May','June','July','August','September','October','November','December','Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
var DAY_NAMES=new Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sun','Mon','Tue','Wed','Thu','Fri','Sat');
function LZ(x) {return(x<0||x>9?"":"0")+x}

// ------------------------------------------------------------------
// isDate ( date_string, format_string )
// Returns true if date string matches format of format string and
// is a valid date. Else returns false.
// It is recommended that you trim whitespace around the value before
// passing it to this function, as whitespace is NOT ignored!
// ------------------------------------------------------------------
function isDate(val,format) {
	var date=getDateFromFormat(val,format);
	if (date==0) { return false; }
	return true;
	}

// -------------------------------------------------------------------
// compareDates(date1,date1format,date2,date2format)
//   Compare two date strings to see which is greater.
//   Returns:
//   1 if date1 is greater than date2
//   0 if date2 is greater than date1 of if they are the same
//  -1 if either of the dates is in an invalid format
// -------------------------------------------------------------------
function compareDates(date1,dateformat1,date2,dateformat2) {
	var d1=getDateFromFormat(date1,dateformat1);
	var d2=getDateFromFormat(date2,dateformat2);
	if (d1==0 || d2==0) {
		return -1;
		}
	else if (d1 > d2) {
		return 1;
		}
	return 0;
	}

// ------------------------------------------------------------------
// formatDate (date_object, format)
// Returns a date in the output format specified.
// The format string uses the same abbreviations as in getDateFromFormat()
// ------------------------------------------------------------------
function formatDate(date,format) {
	format=format+"";
	var result="";
	var i_format=0;
	var c="";
	var token="";
	var y=date.getYear()+"";
	var M=date.getMonth()+1;
	var d=date.getDate();
	var E=date.getDay();
	var H=date.getHours();
	var m=date.getMinutes();
	var s=date.getSeconds();
	var yyyy,yy,MMM,MM,dd,hh,h,mm,ss,ampm,HH,H,KK,K,kk,k;
	// Convert real date parts into formatted versions
	var value=new Object();
	if (y.length < 4) {y=""+(y-0+1900);}
	value["y"]=""+y;
	value["yyyy"]=y;
	value["yy"]=y.substring(2,4);
	value["M"]=M;
	value["MM"]=LZ(M);
	value["MMM"]=MONTH_NAMES[M-1];
	value["NNN"]=MONTH_NAMES[M+11];
	value["d"]=d;
	value["dd"]=LZ(d);
	value["E"]=DAY_NAMES[E+7];
	value["EE"]=DAY_NAMES[E];
	value["H"]=H;
	value["HH"]=LZ(H);
	if (H==0){value["h"]=12;}
	else if (H>12){value["h"]=H-12;}
	else {value["h"]=H;}
	value["hh"]=LZ(value["h"]);
	if (H>11){value["K"]=H-12;} else {value["K"]=H;}
	value["k"]=H+1;
	value["KK"]=LZ(value["K"]);
	value["kk"]=LZ(value["k"]);
	if (H > 11) { value["a"]="PM"; }
	else { value["a"]="AM"; }
	value["m"]=m;
	value["mm"]=LZ(m);
	value["s"]=s;
	value["ss"]=LZ(s);
	while (i_format < format.length) {
		c=format.charAt(i_format);
		token="";
		while ((format.charAt(i_format)==c) && (i_format < format.length)) {
			token += format.charAt(i_format++);
			}
		if (value[token] != null) { result=result + value[token]; }
		else { result=result + token; }
		}
	return result;
	}
	
// ------------------------------------------------------------------
// Utility functions for parsing in getDateFromFormat()
// ------------------------------------------------------------------
function _isInteger(val) {
	var digits="1234567890";
	for (var i=0; i < val.length; i++) {
		if (digits.indexOf(val.charAt(i))==-1) { return false; }
		}
	return true;
	}
function _getInt(str,i,minlength,maxlength) {
	for (var x=maxlength; x>=minlength; x--) {
		var token=str.substring(i,i+x);
		if (token.length < minlength) { return null; }
		if (_isInteger(token)) { return token; }
		}
	return null;
	}
	
// ------------------------------------------------------------------
// getDateFromFormat( date_string , format_string )
//
// This function takes a date string and a format string. It matches
// If the date string matches the format string, it returns the 
// getTime() of the date. If it does not match, it returns 0.
// ------------------------------------------------------------------
function getDateFromFormat(val,format) {
	val=val+"";
	format=format+"";
	var i_val=0;
	var i_format=0;
	var c="";
	var token="";
	var token2="";
	var x,y;
	var now=new Date();
	var year=now.getYear();
	var month=now.getMonth()+1;
	var date=1;
	var hh=now.getHours();
	var mm=now.getMinutes();
	var ss=now.getSeconds();
	var ampm="";
	
	while (i_format < format.length) {
		// Get next token from format string
		c=format.charAt(i_format);
		token="";
		while ((format.charAt(i_format)==c) && (i_format < format.length)) {
			token += format.charAt(i_format++);
			}
		// Extract contents of value based on format token
		if (token=="yyyy" || token=="yy" || token=="y") {
			if (token=="yyyy") { x=4;y=4; }
			if (token=="yy")   { x=2;y=2; }
			if (token=="y")    { x=2;y=4; }
			year=_getInt(val,i_val,x,y);
			if (year==null) { return 0; }
			i_val += year.length;
			if (year.length==2) {
				if (year > 70) { year=1900+(year-0); }
				else { year=2000+(year-0); }
				}
			}
		else if (token=="MMM"||token=="NNN"){
			month=0;
			for (var i=0; i<MONTH_NAMES.length; i++) {
				var month_name=MONTH_NAMES[i];
				if (val.substring(i_val,i_val+month_name.length).toLowerCase()==month_name.toLowerCase()) {
					if (token=="MMM"||(token=="NNN"&&i>11)) {
						month=i+1;
						if (month>12) { month -= 12; }
						i_val += month_name.length;
						break;
						}
					}
				}
			if ((month < 1)||(month>12)){return 0;}
			}
		else if (token=="EE"||token=="E"){
			for (var i=0; i<DAY_NAMES.length; i++) {
				var day_name=DAY_NAMES[i];
				if (val.substring(i_val,i_val+day_name.length).toLowerCase()==day_name.toLowerCase()) {
					i_val += day_name.length;
					break;
					}
				}
			}
		else if (token=="MM"||token=="M") {
			month=_getInt(val,i_val,token.length,2);
			if(month==null||(month<1)||(month>12)){return 0;}
			i_val+=month.length;}
		else if (token=="dd"||token=="d") {
			date=_getInt(val,i_val,token.length,2);
			if(date==null||(date<1)||(date>31)){return 0;}
			i_val+=date.length;}
		else if (token=="hh"||token=="h") {
			hh=_getInt(val,i_val,token.length,2);
			if(hh==null||(hh<1)||(hh>12)){return 0;}
			i_val+=hh.length;}
		else if (token=="HH"||token=="H") {
			hh=_getInt(val,i_val,token.length,2);
			if(hh==null||(hh<0)||(hh>23)){return 0;}
			i_val+=hh.length;}
		else if (token=="KK"||token=="K") {
			hh=_getInt(val,i_val,token.length,2);
			if(hh==null||(hh<0)||(hh>11)){return 0;}
			i_val+=hh.length;}
		else if (token=="kk"||token=="k") {
			hh=_getInt(val,i_val,token.length,2);
			if(hh==null||(hh<1)||(hh>24)){return 0;}
			i_val+=hh.length;hh--;}
		else if (token=="mm"||token=="m") {
			mm=_getInt(val,i_val,token.length,2);
			if(mm==null||(mm<0)||(mm>59)){return 0;}
			i_val+=mm.length;}
		else if (token=="ss"||token=="s") {
			ss=_getInt(val,i_val,token.length,2);
			if(ss==null||(ss<0)||(ss>59)){return 0;}
			i_val+=ss.length;}
		else if (token=="a") {
			if (val.substring(i_val,i_val+2).toLowerCase()=="am") {ampm="AM";}
			else if (val.substring(i_val,i_val+2).toLowerCase()=="pm") {ampm="PM";}
			else {return 0;}
			i_val+=2;}
		else {
			if (val.substring(i_val,i_val+token.length)!=token) {return 0;}
			else {i_val+=token.length;}
			}
		}
	// If there are any trailing characters left in the value, it doesn't match
	if (i_val != val.length) { return 0; }
	// Is date valid for month?
	if (month==2) {
		// Check for leap year
		if ( ( (year%4==0)&&(year%100 != 0) ) || (year%400==0) ) { // leap year
			if (date > 29){ return 0; }
			}
		else { if (date > 28) { return 0; } }
		}
	if ((month==4)||(month==6)||(month==9)||(month==11)) {
		if (date > 30) { return 0; }
		}
	// Correct hours value
	if (hh<12 && ampm=="PM") { hh=hh-0+12; }
	else if (hh>11 && ampm=="AM") { hh-=12; }
	var newdate=new Date(year,month-1,date,hh,mm,ss);
	return newdate.getTime();
	}

// ------------------------------------------------------------------
// parseDate( date_string [, prefer_euro_format] )
//
// This function takes a date string and tries to match it to a
// number of possible date formats to get the value. It will try to
// match against the following international formats, in this order:
// y-M-d   MMM d, y   MMM d,y   y-MMM-d   d-MMM-y  MMM d
// M/d/y   M-d-y      M.d.y     MMM-d     M/d      M-d
// d/M/y   d-M-y      d.M.y     d-MMM     d/M      d-M
// A second argument may be passed to instruct the method to search
// for formats like d/M/y (european format) before M/d/y (American).
// Returns a Date object or null if no patterns match.
// ------------------------------------------------------------------
function parseDate(val) {
	var preferEuro=(arguments.length==2)?arguments[1]:false;
	generalFormats=new Array('y-M-d','MMM d, y','MMM d,y','y-MMM-d','d-MMM-y','MMM d');
	monthFirst=new Array('M/d/y','M-d-y','M.d.y','MMM-d','M/d','M-d');
	dateFirst =new Array('d/M/y','d-M-y','d.M.y','d-MMM','d/M','d-M');
	var checkList=new Array('generalFormats',preferEuro?'dateFirst':'monthFirst',preferEuro?'monthFirst':'dateFirst');
	var d=null;
	for (var i=0; i<checkList.length; i++) {
		var l=window[checkList[i]];
		for (var j=0; j<l.length; j++) {
			d=getDateFromFormat(val,l[j]);
			if (d!=0) { return new Date(d); }
			}
		}
	return null;
	}


/*
 * Date prototype extensions. Doesn't depend on any
 * other code. Doens't overwrite existing methods.
 *
 * Adds dayNames, abbrDayNames, monthNames and abbrMonthNames static properties and isLeapYear,
 * isWeekend, isWeekDay, getDaysInMonth, getDayName, getMonthName, getDayOfYear, getWeekOfYear,
 * setDayOfYear, addYears, addMonths, addDays, addHours, addMinutes, addSeconds methods
 *
 * Copyright (c) 2006 Jörn Zaefferer and Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
 *
 * Additional methods and properties added by Kelvin Luck: firstDayOfWeek, dateFormat, zeroTime, asString, fromString -
 * I've added my name to these methods so you know who to blame if they are broken!
 * 
 * Dual licensed under the MIT and GPL licenses:
 *   http://www.opensource.org/licenses/mit-license.php
 *   http://www.gnu.org/licenses/gpl.html
 *
 */

/**
 * An Array of day names starting with Sunday.
 * 
 * @example dayNames[0]
 * @result 'Sunday'
 *
 * @name dayNames
 * @type Array
 * @cat Plugins/Methods/Date
 */
Date.dayNames = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];

/**
 * An Array of abbreviated day names starting with Sun.
 * 
 * @example abbrDayNames[0]
 * @result 'Sun'
 *
 * @name abbrDayNames
 * @type Array
 * @cat Plugins/Methods/Date
 */
Date.abbrDayNames = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];

/**
 * An Array of month names starting with Janurary.
 * 
 * @example monthNames[0]
 * @result 'January'
 *
 * @name monthNames
 * @type Array
 * @cat Plugins/Methods/Date
 */
Date.monthNames = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

/**
 * An Array of abbreviated month names starting with Jan.
 * 
 * @example abbrMonthNames[0]
 * @result 'Jan'
 *
 * @name monthNames
 * @type Array
 * @cat Plugins/Methods/Date
 */
Date.abbrMonthNames = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

/**
 * The first day of the week for this locale.
 *
 * @name firstDayOfWeek
 * @type Number
 * @cat Plugins/Methods/Date
 * @author Kelvin Luck
 */
Date.firstDayOfWeek = 1;

/**
 * The format that string dates should be represented as (e.g. 'dd/mm/yyyy' for UK, 'mm/dd/yyyy' for US, 'yyyy-mm-dd' for Unicode etc).
 *
 * @name format
 * @type String
 * @cat Plugins/Methods/Date
 * @author Kelvin Luck
 */
Date.format = 'dd/mm/yyyy';
//Date.format = 'mm/dd/yyyy';
//Date.format = 'yyyy-mm-dd';
//Date.format = 'dd mmm yy';

/**
 * The first two numbers in the century to be used when decoding a two digit year. Since a two digit year is ambiguous (and date.setYear
 * only works with numbers < 99 and so doesn't allow you to set years after 2000) we need to use this to disambiguate the two digit year codes.
 *
 * @name format
 * @type String
 * @cat Plugins/Methods/Date
 * @author Kelvin Luck
 */
Date.fullYearStart = '20';

(function() {

	/**
	 * Adds a given method under the given name 
	 * to the Date prototype if it doesn't
	 * currently exist.
	 *
	 * @private
	 */
	function add(name, method) {
		if( !Date.prototype[name] ) {
			Date.prototype[name] = method;
		}
	};
	
	/**
	 * Checks if the year is a leap year.
	 *
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.isLeapYear();
	 * @result true
	 *
	 * @name isLeapYear
	 * @type Boolean
	 * @cat Plugins/Methods/Date
	 */
	add("isLeapYear", function() {
		var y = this.getFullYear();
		return (y%4==0 && y%100!=0) || y%400==0;
	});
	
	/**
	 * Checks if the day is a weekend day (Sat or Sun).
	 *
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.isWeekend();
	 * @result false
	 *
	 * @name isWeekend
	 * @type Boolean
	 * @cat Plugins/Methods/Date
	 */
	add("isWeekend", function() {
		return this.getDay()==0 || this.getDay()==6;
	});
	
	/**
	 * Check if the day is a day of the week (Mon-Fri)
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.isWeekDay();

	 * @result false
	 * 
	 * @name isWeekDay
	 * @type Boolean
	 * @cat Plugins/Methods/Date
	 */
	add("isWeekDay", function() {
		return !this.isWeekend();
	});
	
	/**
	 * Gets the number of days in the month.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getDaysInMonth();
	 * @result 31
	 * 
	 * @name getDaysInMonth
	 * @type Number
	 * @cat Plugins/Methods/Date
	 */
	add("getDaysInMonth", function() {
		return [31,(this.isLeapYear() ? 29:28),31,30,31,30,31,31,30,31,30,31][this.getMonth()];
	});
	
	/**
	 * Gets the name of the day.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getDayName();
	 * @result 'Saturday'
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getDayName(true);
	 * @result 'Sat'
	 * 
	 * @param abbreviated Boolean When set to true the name will be abbreviated.
	 * @name getDayName
	 * @type String
	 * @cat Plugins/Methods/Date
	 */
	add("getDayName", function(abbreviated) {
		return abbreviated ? Date.abbrDayNames[this.getDay()] : Date.dayNames[this.getDay()];
	});

	/**
	 * Gets the name of the month.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getMonthName();
	 * @result 'Janurary'
	 *
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getMonthName(true);
	 * @result 'Jan'
	 * 
	 * @param abbreviated Boolean When set to true the name will be abbreviated.
	 * @name getDayName
	 * @type String
	 * @cat Plugins/Methods/Date
	 */
	add("getMonthName", function(abbreviated) {
		return abbreviated ? Date.abbrMonthNames[this.getMonth()] : Date.monthNames[this.getMonth()];
	});

	/**
	 * Get the number of the day of the year.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getDayOfYear();
	 * @result 11
	 * 
	 * @name getDayOfYear
	 * @type Number
	 * @cat Plugins/Methods/Date
	 */
	add("getDayOfYear", function() {
		var tmpdtm = new Date("1/1/" + this.getFullYear());
		return Math.floor((this.getTime() - tmpdtm.getTime()) / 86400000);
	});
	
	/**
	 * Get the number of the week of the year.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.getWeekOfYear();
	 * @result 2
	 * 
	 * @name getWeekOfYear
	 * @type Number
	 * @cat Plugins/Methods/Date
	 */
	add("getWeekOfYear", function() {
		return Math.ceil(this.getDayOfYear() / 7);
	});

	/**
	 * Set the day of the year.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.setDayOfYear(1);
	 * dtm.toString();
	 * @result 'Tue Jan 01 2008 00:00:00'
	 * 
	 * @name setDayOfYear
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("setDayOfYear", function(day) {
		this.setMonth(0);
		this.setDate(day);
		return this;
	});
	
	/**
	 * Add a number of years to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addYears(1);
	 * dtm.toString();
	 * @result 'Mon Jan 12 2009 00:00:00'
	 * 
	 * @name addYears
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addYears", function(num) {
		this.setFullYear(this.getFullYear() + num);
		return this;
	});
	
	/**
	 * Add a number of months to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addMonths(1);
	 * dtm.toString();
	 * @result 'Tue Feb 12 2008 00:00:00'
	 * 
	 * @name addMonths
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addMonths", function(num) {
		var tmpdtm = this.getDate();
		
		this.setMonth(this.getMonth() + num);
		
		if (tmpdtm > this.getDate())
			this.addDays(-this.getDate());
		
		return this;
	});
	
	/**
	 * Add a number of days to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addDays(1);
	 * dtm.toString();
	 * @result 'Sun Jan 13 2008 00:00:00'
	 * 
	 * @name addDays
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addDays", function(num) {
		//this.setDate(this.getDate() + num);
		this.setTime(this.getTime() + (num*86400000) );
		return this;
	});
	
	/**
	 * Add a number of hours to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addHours(24);
	 * dtm.toString();
	 * @result 'Sun Jan 13 2008 00:00:00'
	 * 
	 * @name addHours
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addHours", function(num) {
		this.setHours(this.getHours() + num);
		return this;
	});

	/**
	 * Add a number of minutes to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addMinutes(60);
	 * dtm.toString();
	 * @result 'Sat Jan 12 2008 01:00:00'
	 * 
	 * @name addMinutes
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addMinutes", function(num) {
		this.setMinutes(this.getMinutes() + num);
		return this;
	});
	
	/**
	 * Add a number of seconds to the date object.
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.addSeconds(60);
	 * dtm.toString();
	 * @result 'Sat Jan 12 2008 00:01:00'
	 * 
	 * @name addSeconds
	 * @type Date
	 * @cat Plugins/Methods/Date
	 */
	add("addSeconds", function(num) {
		this.setSeconds(this.getSeconds() + num);
		return this;
	});
	
	/**
	 * Sets the time component of this Date to zero for cleaner, easier comparison of dates where time is not relevant.
	 * 
	 * @example var dtm = new Date();
	 * dtm.zeroTime();
	 * dtm.toString();
	 * @result 'Sat Jan 12 2008 00:01:00'
	 * 
	 * @name zeroTime
	 * @type Date
	 * @cat Plugins/Methods/Date
	 * @author Kelvin Luck
	 */
	add("zeroTime", function() {
		this.setMilliseconds(0);
		this.setSeconds(0);
		this.setMinutes(0);
		this.setHours(0);
		return this;
	});
	
	/**
	 * Returns a string representation of the date object according to Date.format.
	 * (Date.toString may be used in other places so I purposefully didn't overwrite it)
	 * 
	 * @example var dtm = new Date("01/12/2008");
	 * dtm.asString();
	 * @result '12/01/2008' // (where Date.format == 'dd/mm/yyyy'
	 * 
	 * @name asString
	 * @type Date
	 * @cat Plugins/Methods/Date
	 * @author Kelvin Luck
	 */
	add("asString", function(format) {
		var r = format || Date.format;
		return r
			.split('yyyy').join(this.getFullYear())
			.split('yy').join((this.getFullYear() + '').substring(2))
			.split('mmmm').join(this.getMonthName(false))
			.split('mmm').join(this.getMonthName(true))
			.split('mm').join(_zeroPad(this.getMonth()+1))
			.split('dd').join(_zeroPad(this.getDate()))
			.split('hh').join(_zeroPad(this.getHours()))
			.split('min').join(_zeroPad(this.getMinutes()))
			.split('ss').join(_zeroPad(this.getSeconds()));
	});
	
	/**
	 * Returns a new date object created from the passed String according to Date.format or false if the attempt to do this results in an invalid date object
	 * (We can't simple use Date.parse as it's not aware of locale and I chose not to overwrite it incase it's functionality is being relied on elsewhere)
	 *
	 * @example var dtm = Date.fromString("12/01/2008");
	 * dtm.toString();
	 * @result 'Sat Jan 12 2008 00:00:00' // (where Date.format == 'dd/mm/yyyy'
	 * 
	 * @name fromString
	 * @type Date
	 * @cat Plugins/Methods/Date
	 * @author Kelvin Luck
	 */
	Date.fromString = function(s, format)
	{
		var f = format || Date.format;
		var d = new Date('01/01/1977');
		
		var mLength = 0;

		var iM = f.indexOf('mmmm');
		if (iM > -1) {
			for (var i=0; i<Date.monthNames.length; i++) {
				var mStr = s.substr(iM, Date.monthNames[i].length);
				if (Date.monthNames[i] == mStr) {
					mLength = Date.monthNames[i].length - 4;
					break;
				}
			}
			d.setMonth(i);
		} else {
			iM = f.indexOf('mmm');
			if (iM > -1) {
				var mStr = s.substr(iM, 3);
				for (var i=0; i<Date.abbrMonthNames.length; i++) {
					if (Date.abbrMonthNames[i] == mStr) break;
				}
				d.setMonth(i);
			} else {
				d.setMonth(Number(s.substr(f.indexOf('mm'), 2)) - 1);
			}
		}
		
		var iY = f.indexOf('yyyy');

		if (iY > -1) {
			if (iM < iY)
			{
				iY += mLength;
			}
			d.setFullYear(Number(s.substr(iY, 4)));
		} else {
			if (iM < iY)
			{
				iY += mLength;
			}
			// TODO - this doesn't work very well - are there any rules for what is meant by a two digit year?
			d.setFullYear(Number(Date.fullYearStart + s.substr(f.indexOf('yy'), 2)));
		}
		var iD = f.indexOf('dd');
		if (iM < iD)
		{
			iD += mLength;
		}
		d.setDate(Number(s.substr(iD, 2)));
		if (isNaN(d.getTime())) {
			return false;
		}
		return d;
	};
	
	// utility method
	var _zeroPad = function(num) {
		var s = '0'+num;
		return s.substring(s.length-2)
		//return ('0'+num).substring(-2); // doesn't work on IE :(
	};
	
})();