Array.prototype.exists = function (x) {
    for (var i = 0; i < this.length; i++) {
        if (this[i] == x) return true;
    }
    return false;
}

Date.prototype.formatDate = function (locale,input,time) {
    // formatDate :
    // a PHP date like function, for formatting date strings
    // See: http://www.php.net/date
    //
    // input : format string
    // time : epoch time (seconds, and optional)
    //
    // if time is not passed, formatting is based on 
    // the current "this" date object's set time.
    //
    // supported:
    // a, A, B, d, D, F, g, G, h, H, i, j, l (lowercase L), L, 
    // m, M, n, O, r, s, S, t, U, w, W, y, Y, z, c
    //
    // unsupported:
    // I (capital i), T, Z    

    var lang = locale;

    var supportedLang = ["en", "zh"]; 
    
    var switches =    ["a", "A", "B", "d", "D", "F", "g", "G", "h", "H", 
                       "i", "j", "l", "L", "m", "M", "n", "O", "r", "s", 
                       "S", "t", "U", "w", "W", "y", "Y", "z", "c"];
    var meridiemLower_en = ["am", "pm"];
    var meridiemLower_zh = ["上午", "下午"];
    var meridiemUpper_en = ["AM", "PM"];
    var meridiemUpper_zh = ["上午", "下午"];
    var daysLong_en =    ["Sunday", "Monday", "Tuesday", "Wednesday", 
                          "Thursday", "Friday", "Saturday"];
    var daysLong_zh =    ["星期日", "星期一", "星期二", "星期三", 
                          "星期四", "星期五", "星期六"];
    var daysShort_en =   ["Sun", "Mon", "Tue", "Wed", 
                          "Thu", "Fri", "Sat"];
    var daysShort_zh =    ["星期日", "星期一", "星期二", "星期三", 
                          "星期四", "星期五", "星期六"];
    var monthsShort_en = ["Jan", "Feb", "Mar", "Apr",
                          "May", "Jun", "Jul", "Aug", "Sep",
                          "Oct", "Nov", "Dec"];
    var monthsShort_zh = ["一月", "二月", "三月", "四月",
                          "五月", "六月", "七月", "八月", "九月",
                          "十月", "十一月", "十二月"];
    var monthsLong_en =  ["January", "February", "March", "April",
                          "May", "June", "July", "August", "September",
                          "October", "November", "December"];
    var monthsLong_zh = ["一月", "二月", "三月", "四月",
                         "五月", "六月", "七月", "八月", "九月",
                         "十月", "十一月", "十二月"];
    var daysSuffix = ["st", "nd", "rd", "th", "th", "th", "th", // 1st - 7th
                      "th", "th", "th", "th", "th", "th", "th", // 8th - 14th
                      "th", "th", "th", "th", "th", "th", "st", // 15th - 21st
                      "nd", "rd", "th", "th", "th", "th", "th", // 22nd - 28th
                      "th", "th", "st"];                        // 29th - 31st

    function a() {
        // Lowercase Ante meridiem and Post meridiem
        var a = eval("meridiemLower_" + lang);
        return self.getHours() > 11? a[1] : a[0];
    }
    function A() {
        // Uppercase Ante meridiem and Post meridiem
        var a = eval("meridiemUpper_" + lang);
        return self.getHours() > 11? a[1] : a[0];
    }

    function B(){
        // Swatch internet time. code simply grabbed from ppk,
        // since I was feeling lazy:
        // http://www.xs4all.nl/~ppk/js/beat.html
        var off = (self.getTimezoneOffset() + 60)*60;
        var theSeconds = (self.getHours() * 3600) + 
                         (self.getMinutes() * 60) + 
                          self.getSeconds() + off;
        var beat = Math.floor(theSeconds/86.4);
        if (beat > 1000) beat -= 1000;
        if (beat < 0) beat += 1000;
        if ((""+beat).length == 1) beat = "00"+beat;
        if ((""+beat).length == 2) beat = "0"+beat;
        return beat;
    }
    
    function c() {
        // custom formatted date
        var c; // result

        if (lang == "en") {
            //  Dec         21     ,     02
            c = M() + " " + d() + ", " + y() +
            //        16     :    01     :    07
                " " + H() + ":" + i() + ":" + s();
        } else if (lang == "zh") {
            //  2002   年    12     月    21     日
            c = Y() + "年" + m() + "月" + d() + "日 " +
            //        16     :    01     :    07
                " " + H() + ":" + i() + ":" + s();
        }
        return c;
    }

    function d() {
        // Day of the month, 2 digits with leading zeros
        return new String(self.getDate()).length == 1?
        "0"+self.getDate() : self.getDate();
    }
    function D() {
        // A textual representation of a day, three letters
        var a = eval("daysShort_" + lang);
        return a[self.getDay()];
    }

    function F() {
        // A full textual representation of a month
        var a = eval("monthsLong_" + lang);
        return a[self.getMonth()];
    }

    function g() {
        // 12-hour format of an hour without leading zeros
        return self.getHours() > 12? self.getHours()-12 : self.getHours();
    }
    function G() {
        // 24-hour format of an hour without leading zeros
        return self.getHours();
    }

    function h() {
        // 12-hour format of an hour with leading zeros
        if (self.getHours() > 12) {
          var s = new String(self.getHours()-12);
          return s.length == 1?
          "0"+ (self.getHours()-12) : self.getHours()-12;
        } else { 
          var s = new String(self.getHours());
          return s.length == 1?
          "0"+self.getHours() : self.getHours();
        }  
    }
    function H() {
        // 24-hour format of an hour with leading zeros
        return new String(self.getHours()).length == 1?
        "0"+self.getHours() : self.getHours();
    }

    function i() {
        // Minutes with leading zeros
        return new String(self.getMinutes()).length == 1? 
        "0"+self.getMinutes() : self.getMinutes(); 
    }

    function j() {
        // Day of the month without leading zeros
        return self.getDate();
    }    

    function l() {
        // A full textual representation of the day of the week
        var a = eval("daysLong_" + lang);
        return a[self.getDay()];
    }
    function L() {
        // leap year or not. 1 if leap year, 0 if not.
        // the logic should match iso's 8601 standard.
        var y_ = Y();
        if (         
            (y_ % 4 == 0 && y_ % 100 != 0) ||
            (y_ % 4 == 0 && y_ % 100 == 0 && y_ % 400 == 0)
            ) {
            return 1;
        } else {
            return 0;
        }
    }

    function m() {
        // Numeric representation of a month, with leading zeros
        return self.getMonth() < 9?
        "0"+(self.getMonth()+1) : 
        self.getMonth()+1;
    }
    function M() {
        // A short textual representation of a month, three letters
        var a = eval("monthsShort_" + lang);
        return a[self.getMonth()];
    }

    function n() {
        // Numeric representation of a month, without leading zeros
        return self.getMonth()+1;
    }

    function O() {
        // Difference to Greenwich time (GMT) in hours
        var os = Math.abs(self.getTimezoneOffset());
        var h = ""+Math.floor(os/60);
        var m = ""+(os%60);
        h.length == 1? h = "0"+h:1;
        m.length == 1? m = "0"+m:1;
        return self.getTimezoneOffset() < 0 ? "+"+h+m : "-"+h+m;
    }

    function r() {
        // RFC 822 formatted date
        var r; // result

        if (lang == "en") {
            //  Thu    ,     21          Dec         2000
            r = D() + ", " + d() + " " + M() + " " + Y() +
            //        16     :    01     :    07          +0200
                " " + H() + ":" + i() + ":" + s() + " " + O();
        } else if (lang == "zh") {
            //  2000   年    12     月    21     日     Thu
            r = Y() + "年" + m() + "月" + d() + "日 " + D() +
            //        16     :    01     :    07          +0200
                " " + H() + ":" + i() + ":" + s() + " " + O();
        }
        return r;
    }

    function s() {
        // Seconds, with leading zeros
        return new String(self.getSeconds()).length == 1?
        "0"+self.getSeconds() : self.getSeconds();
    }
    function S() {
        // English ordinal suffix for the day of the month, 2 characters
        return daysSuffix[self.getDate()-1];
    }

    function t() {

        // thanks to Matt Bannon for some much needed code-fixes here!
        var daysinmonths = [null,31,28,31,30,31,30,31,31,30,31,30,31];
        if (L()==1 && n()==2) return 29; // leap day
        return daysinmonths[n()];
    }

    function U() {
        // Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)
        return Math.round(self.getTime()/1000);
    }

    function w() {
        // Numeric representation of the day of the week
        return self.getDay();
    }
    function W() {
        // Weeknumber, as per ISO specification:
        // http://www.cl.cam.ac.uk/~mgk25/iso-time.html
        
        // if the day is three days before newyears eve,
        // there's a chance it's "week 1" of next year.
        // here we check for that.
        var beforeNY = 364+L() - z();
        var afterNY  = z();
        var weekday = w()!=0?w()-1:6; // makes sunday (0), into 6.
        if (beforeNY <= 2 && weekday <= 2-beforeNY) {
            return 1;
        }
        // similarly, if the day is within threedays of newyears
        // there's a chance it belongs in the old year.
        var ny = new Date("January 1 " + Y() + " 00:00:00");
        var nyDay = ny.getDay()!=0?ny.getDay()-1:6;
        if (
            (afterNY <= 2) && 
            (nyDay >=4)  && 
            (afterNY >= (6-nyDay))
            ) {
            // Since I'm not sure we can just always return 53,
            // i call the function here again, using the last day
            // of the previous year, as the date, and then just
            // return that week.
            var prevNY = new Date("December 31 " + (Y()-1) + " 00:00:00");
            return prevNY.formatDate("W");
        }
        
        // week 1, is the week that has the first thursday in it.
        // note that this value is not zero index.
        if (nyDay <= 3) {
            // first day of the year fell on a thursday, or earlier.
            return 1 + Math.floor( ( z() + nyDay ) / 7 );
        } else {
            // first day of the year fell on a friday, or later.
            return 1 + Math.floor( ( z() - ( 7 - nyDay ) ) / 7 );
        }
    }
    
    function y() {
        // A two-digit representation of a year
        var y = Y()+"";
        return y.substring(y.length-2,y.length);
    }
    function Y() {
        // A full numeric representation of a year, 4 digits

        // we first check, if getFullYear is supported. if it
        // is, we just use that. ppks code is nice, but wont
        // work with dates outside 1900-2038, or something like that
        if (self.getFullYear) {
            var newDate = new Date("January 1 2001 00:00:00 +0000");
            var x = newDate .getFullYear();
            if (x == 2001) {              
                // i trust the method now
                return self.getFullYear();
            }
        }
        // else, do this:
        // codes thanks to ppk:
        // http://www.xs4all.nl/~ppk/js/introdate.html
        var x = self.getYear();
        var y = x % 100;
        y += (y < 38) ? 2000 : 1900;
        return y;
    }

    function z() {
        // The day of the year, zero indexed! 0 through 366
        var t = new Date("January 1 " + Y() + " 00:00:00");
        var diff = self.getTime() - t.getTime();
        return Math.floor(diff/1000/60/60/24);
    }
        
    if (!supportedLang.exists(lang)) lang = "en";

    var self = this;
    if (time) {
        // save time
        var prevTime = self.getTime();
        self.setTime(time);
    }
    
    var ia = input.split("");
    var ij = 0;
    while (ia[ij]) {
        if (ia[ij] == "\\") {
            // this is our way of allowing users to escape stuff
            ia.splice(ij,1);
        } else {
            if (switches.exists(ia[ij])) {
                ia[ij] = eval(ia[ij] + "()");
            }
        }
        ij++;
    }
    // reset time, back to what it was
    if (prevTime) {
        self.setTime(prevTime);
    }
    return ia.join("");
}