    /*
     * All the Date functions below are the excellent work of Baron Schwartz
     * They generate precompiled functions from date formats instead of parsing and processing
     * the format everytime you do something with a date.
     */
    // holder
    /** @ignore */
    Date.parseFunctions = {count:0};
    /** @ignore */
    Date.parseRegexes = [];
    /** @ignore */
    Date.formatFunctions = {count:0};

    /**
     * Formats a date given to the supplied format - the format syntax is the same as <a href="http://www.php.net/date">PHP's date() function</a>.
     */
    Date.prototype.dateFormat = function(format) {
        if (Date.formatFunctions[format] == null) {
            Date.createNewFormat(format);
        }
        var func = Date.formatFunctions[format];
        return this[func]();
    };

    /**
     * Same as {@link #dateFormat}
     */
    Date.prototype.format = Date.prototype.dateFormat;

    /** @ignore */
    Date.createNewFormat = function(format) {
        var funcName = "format" + Date.formatFunctions.count++;
        Date.formatFunctions[format] = funcName;
        var code = "Date.prototype." + funcName + " = function(){return ";
        var special = false;
        var ch = '';
        for (var i = 0; i < format.length; ++i) {
            ch = format.charAt(i);
            if (!special && ch == "\\") {
                special = true;
            }
            else if (special) {
                special = false;
                code += "'" + String.escape(ch) + "' + ";
            }
            else {
                code += Date.getFormatCode(ch);
            }
        }
        eval(code.substring(0, code.length - 3) + ";}");
    };

    /** @ignore */
    Date.getFormatCode = function(character) {
        switch (character) {
        case "d":
            return "String.leftPad(this.getDate(), 2, '0') + ";
        case "D":
            return "Date.dayNames[this.getDay()].substring(0, 3) + ";
        case "j":
            return "this.getDate() + ";
        case "l":
            return "Date.dayNames[this.getDay()] + ";
        case "S":
            return "this.getSuffix() + ";
        case "w":
            return "this.getDay() + ";
        case "z":
            return "this.getDayOfYear() + ";
        case "W":
            return "this.getWeekOfYear() + ";
        case "F":
            return "Date.monthNames[this.getMonth()] + ";
        case "m":
            return "String.leftPad(this.getMonth() + 1, 2, '0') + ";
        case "M":
            return "Date.monthNames[this.getMonth()].substring(0, 3) + ";
        case "n":
            return "(this.getMonth() + 1) + ";
        case "t":
            return "this.getDaysInMonth() + ";
        case "L":
            return "(this.isLeapYear() ? 1 : 0) + ";
        case "Y":
            return "this.getFullYear() + ";
        case "y":
            return "('' + this.getFullYear()).substring(2, 4) + ";
        case "a":
            return "(this.getHours() < 12 ? 'am' : 'pm') + ";
        case "A":
            return "(this.getHours() < 12 ? 'AM' : 'PM') + ";
        case "g":
            return "((this.getHours() %12) ? this.getHours() % 12 : 12) + ";
        case "G":
            return "this.getHours() + ";
        case "h":
            return "String.leftPad((this.getHours() %12) ? this.getHours() % 12 : 12, 2, '0') + ";
        case "H":
            return "String.leftPad(this.getHours(), 2, '0') + ";
        case "i":
            return "String.leftPad(this.getMinutes(), 2, '0') + ";
        case "s":
            return "String.leftPad(this.getSeconds(), 2, '0') + ";
        case "O":
            return "this.getGMTOffset() + ";
        case "T":
            return "this.getTimezone() + ";
        case "Z":
            return "(this.getTimezoneOffset() * -60) + ";
        default:
            return "'" + String.escape(character) + "' + ";
        };
    };

    /**
     * Parses a date given the supplied format - the format syntax is the same as <a href="http://www.php.net/date">PHP's date() function</a>.
     */
    Date.parseDate = function(input, format) {
        if (Date.parseFunctions[format] == null) {
            Date.createParser(format);
        }
        var func = Date.parseFunctions[format];
        return Date[func](input);
    };

    /** @ignore */
    Date.createParser = function(format) {
        var funcName = "parse" + Date.parseFunctions.count++;
        var regexNum = Date.parseRegexes.length;
        var currentGroup = 1;
        Date.parseFunctions[format] = funcName;

        var code = "Date." + funcName + " = function(input){\n"
            + "var y = -1, m = -1, d = -1, h = -1, i = -1, s = -1;\n"
            + "var d = new Date();\n"
            + "y = d.getFullYear();\n"
            + "m = d.getMonth();\n"
            + "d = d.getDate();\n"
            + "var results = input.match(Date.parseRegexes[" + regexNum + "]);\n"
            + "if (results && results.length > 0) {"
        var regex = "";

        var special = false;
        var ch = '';
        for (var i = 0; i < format.length; ++i) {
            ch = format.charAt(i);
            if (!special && ch == "\\") {
                special = true;
            }
            else if (special) {
                special = false;
                regex += String.escape(ch);
            }
            else {
                obj = Date.formatCodeToRegex(ch, currentGroup);
                currentGroup += obj.g;
                regex += obj.s;
                if (obj.g && obj.c) {
                    code += obj.c;
                }
            }
        }

        code += "if (y > 0 && m >= 0 && d > 0 && h >= 0 && i >= 0 && s >= 0)\n"
            + "{return new Date(y, m, d, h, i, s);}\n"
            + "else if (y > 0 && m >= 0 && d > 0 && h >= 0 && i >= 0)\n"
            + "{return new Date(y, m, d, h, i);}\n"
            + "else if (y > 0 && m >= 0 && d > 0 && h >= 0)\n"
            + "{return new Date(y, m, d, h);}\n"
            + "else if (y > 0 && m >= 0 && d > 0)\n"
            + "{return new Date(y, m, d);}\n"
            + "else if (y > 0 && m >= 0)\n"
            + "{return new Date(y, m);}\n"
            + "else if (y > 0)\n"
            + "{return new Date(y);}\n"
            + "}return null;}";

        Date.parseRegexes[regexNum] = new RegExp("^" + regex + "$");
        eval(code);
    };

    /** @ignore */
    Date.formatCodeToRegex = function(character, currentGroup) {
        switch (character) {
        case "D":
            return {g:0,
            c:null,
            s:"(?:Sun|Mon|Tue|Wed|Thu|Fri|Sat)"};
        case "j":
        case "d":
            return {g:1,
                c:"d = parseInt(results[" + currentGroup + "], 10);\n",
                s:"(\\d{1,2})"};
        case "l":
            return {g:0,
                c:null,
                s:"(?:" + Date.dayNames.join("|") + ")"};
        case "S":
            return {g:0,
                c:null,
                s:"(?:st|nd|rd|th)"};
        case "w":
            return {g:0,
                c:null,
                s:"\\d"};
        case "z":
            return {g:0,
                c:null,
                s:"(?:\\d{1,3})"};
        case "W":
            return {g:0,
                c:null,
                s:"(?:\\d{2})"};
        case "F":
            return {g:1,
                c:"m = parseInt(Date.monthNumbers[results[" + currentGroup + "].substring(0, 3)], 10);\n",
                s:"(" + Date.monthNames.join("|") + ")"};
        case "M":
            return {g:1,
                c:"m = parseInt(Date.monthNumbers[results[" + currentGroup + "]], 10);\n",
                s:"(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)"};
        case "n":
        case "m":
            return {g:1,
                c:"m = parseInt(results[" + currentGroup + "], 10) - 1;\n",
                s:"(\\d{1,2})"};
        case "t":
            return {g:0,
                c:null,
                s:"\\d{1,2}"};
        case "L":
            return {g:0,
                c:null,
                s:"(?:1|0)"};
        case "Y":
            return {g:1,
                c:"y = parseInt(results[" + currentGroup + "], 10);\n",
                s:"(\\d{4})"};
        case "y":
            return {g:1,
                c:"var ty = parseInt(results[" + currentGroup + "], 10);\n"
                    + "y = ty > Date.y2kYear ? 1900 + ty : 2000 + ty;\n",
                s:"(\\d{1,2})"};
        case "a":
            return {g:1,
                c:"if (results[" + currentGroup + "] == 'am') {\n"
                    + "if (h == 12) { h = 0; }\n"
                    + "} else { if (h < 12) { h += 12; }}",
                s:"(am|pm)"};
        case "A":
            return {g:1,
                c:"if (results[" + currentGroup + "] == 'AM') {\n"
                    + "if (h == 12) { h = 0; }\n"
                    + "} else { if (h < 12) { h += 12; }}",
                s:"(AM|PM)"};
        case "g":
        case "G":
        case "h":
        case "H":
            return {g:1,
                c:"h = parseInt(results[" + currentGroup + "], 10);\n",
                s:"(\\d{1,2})"};
        case "i":
            return {g:1,
                c:"i = parseInt(results[" + currentGroup + "], 10);\n",
                s:"(\\d{2})"};
        case "s":
            return {g:1,
                c:"s = parseInt(results[" + currentGroup + "], 10);\n",
                s:"(\\d{2})"};
        case "O":
            return {g:0,
                c:null,
                s:"[+-]\\d{4}"};
        case "T":
            return {g:0,
                c:null,
                s:"[A-Z]{3}"};
        case "Z":
            return {g:0,
                c:null,
                s:"[+-]\\d{1,5}"};
        default:
            return {g:0,
                c:null,
                s:String.escape(character)};
        }
    };

    Date.prototype.getTimezone = function() {
        return this.toString().replace(
            /^.*? ([A-Z]{3}) [0-9]{4}.*$/, "$1").replace(
            /^.*?\(([A-Z])[a-z]+ ([A-Z])[a-z]+ ([A-Z])[a-z]+\)$/, "$1$2$3");
    };

    Date.prototype.getGMTOffset = function() {
        return (this.getTimezoneOffset() > 0 ? "-" : "+")
            + String.leftPad(Math.floor(this.getTimezoneOffset() / 60), 2, "0")
            + String.leftPad(this.getTimezoneOffset() % 60, 2, "0");
    };

    Date.prototype.getDayOfYear = function() {
        var num = 0;
        Date.daysInMonth[1] = this.isLeapYear() ? 29 : 28;
        for (var i = 0; i < this.getMonth(); ++i) {
            num += Date.daysInMonth[i];
        }
        return num + this.getDate() - 1;
    };

    Date.prototype.getWeekOfYear = function() {
        // Skip to Thursday of this week
        var now = this.getDayOfYear() + (4 - this.getDay());
        // Find the first Thursday of the year
        var jan1 = new Date(this.getFullYear(), 0, 1);
        var then = (7 - jan1.getDay() + 4);
        document.write(then);
        return String.leftPad(((now - then) / 7) + 1, 2, "0");
    };

    Date.prototype.isLeapYear = function() {
        var year = this.getFullYear();
        return ((year & 3) == 0 && (year % 100 || (year % 400 == 0 && year)));
    };

    Date.prototype.getFirstDayOfMonth = function() {
        var day = (this.getDay() - (this.getDate() - 1)) % 7;
        return (day < 0) ? (day + 7) : day;
    };

    Date.prototype.getLastDayOfMonth = function() {
        var day = (this.getDay() + (Date.daysInMonth[this.getMonth()] - this.getDate())) % 7;
        return (day < 0) ? (day + 7) : day;
    };

    Date.prototype.getDaysInMonth = function() {
        Date.daysInMonth[1] = this.isLeapYear() ? 29 : 28;
        return Date.daysInMonth[this.getMonth()];
    };

    /** @ignore */
    Date.prototype.getSuffix = function() {
        switch (this.getDate()) {
            case 1:
            case 21:
            case 31:
                return "st";
            case 2:
            case 22:
                return "nd";
            case 3:
            case 23:
                return "rd";
            default:
                return "th";
        }
    };

    /** @ignore */
    Date.daysInMonth = [31,28,31,30,31,30,31,31,30,31,30,31];

    /**
     * Override these values for international dates, for example...
     * Date.monthNames = ['JanInYourLang', 'FebInYourLang', ...];
     */
    Date.monthNames =
       ["January",
        "February",
        "March",
        "April",
        "May",
        "June",
        "July",
        "August",
        "September",
        "October",
        "November",
        "December"];

    /**
     * Override these values for international dates, for example...
     * Date.dayNames = ['SundayInYourLang', 'MondayInYourLang', ...];
     */
    Date.dayNames =
       ["Sunday",
        "Monday",
        "Tuesday",
        "Wednesday",
        "Thursday",
        "Friday",
        "Saturday"];

    /** @ignore */
    Date.y2kYear = 50;

    /** @ignore */
    Date.monthNumbers = {
        Jan:0,
        Feb:1,
        Mar:2,
        Apr:3,
        May:4,
        Jun:5,
        Jul:6,
        Aug:7,
        Sep:8,
        Oct:9,
        Nov:10,
        Dec:11};

Copyright © 2006 Jack Slocum. All rights reserved.