Data.prototype.format

    if(!Date.prototype.format) {

        //Formats a JavaScript Date object to a string.
        //Following PHP's date() format --
        //http://php.net/manual/en/function.date.php
        Date.prototype.format = (function () {

            var pattern = {

                    //Day of the month, 2 digits with leading zeros
                    d: function () {
                        var day = this.getDate();
                        return day < 10 ? '0' + day : day;
                    },

                    //A textual representation of a day, three letters
                    D: function () {
                        return pattern['l'].call(this).slice(0,3);
                    },

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

                    //A full textual representation of the day of the week
                    l: function () {
                        switch(this.getDay()) {
                        case 0:
                            return 'Sunday';
                        case 1:
                            return 'Monday';
                        case 2:
                            return 'Tuesday';
                        case 3:
                            return 'Wednesday';
                        case 4:
                            return 'Thursday';
                        case 5:
                            return 'Friday';
                        case 6:
                            return 'Saturday';
                        }
                    },

                    //ISO-8601 numeric representation of the day of the week
                    N: function () {
                        return this.getDay() === 0 ? 7 : this.getDay();
                    },

                    //English ordinal suffix for the day of the month, 2 characters
                    S: function () {

                        if(this.getDate() > 3 && this.getDate() < 21) {
                            return 'th';
                        }

                        switch(this.getDate().toString().slice(-1)) {
                        case '1':
                            return 'st';
                        case '2':
                            return 'nd';
                        case '3':
                            return 'rd';
                        default:
                            return 'th';
                        }
                    },

                    //Numeric representation of the day of the week
                    w: function () {
                        return this.getDay();
                    },

                    //The day of the year (starting from 0)
                    z: function () {
                        return Math.floor(((this - new Date(this.getFullYear(), 0, 1)) / 86400000), 0);
                    },

                    //ISO-8601 week number of year, weeks starting on Monday
                    W: function () {
                        var start = new Date(this.getFullYear(), 0, 1);
                        return Math.ceil((((this - start) / 86400000) + start.getDay() + 1) / 7);
                    },

                    //A full textual representation of a month, such as January or March
                    F: function () {
                        switch(this.getMonth()) {
                        case 0:
                            return 'January';
                        case 1:
                            return 'February';
                        case 2:
                            return 'March';
                        case 3:
                            return 'April';
                        case 4:
                            return 'May';
                        case 5:
                            return 'June';
                        case 6:
                            return 'July';
                        case 7:
                            return 'August';
                        case 8:
                            return 'September';
                        case 9:
                            return 'October';
                        case 10:
                            return 'November';
                        case 11:
                            return 'December';
                        }
                    },

                    //Numeric representation of a month, with leading zeros
                    m: function () {
                        var month = this.getMonth()+1;
                        return month < 10 ? '0' + month : month;
                    },

                    //A short textual representation of a month, three letters
                    M: function () {
                        return pattern['F'].call(this).slice(0,3);
                    },

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

                    //Number of days in the given month
                    t: function () {
                        return 32 - new Date(this.getFullYear(), this.getMonth(), 32).getDate();
                    },

                    //Whether it's a leap year
                    L: function () {
                        return new Date(this.getFullYear(), 1, 29).getDate() === 29 ? 1 : 0;
                    },

                    //ISO-8601 year number. This has the same value as Y, except that if the ISO week number (W) belongs to the previous or next year, that year is used instead.
                    O: function () {
                        return null;
                    },

                    //A full numeric representation of a year, 4 digits
                    Y: function () {
                        return this.getFullYear();
                    },

                    //A two digit representation of a year
                    y: function () {
                        return this.getFullYear().toString().slice(-2);
                    },

                    //Lowercase Ante meridiem and Post meridiem
                    a: function () {
                        return this.getHours() < 12 ? 'am' : 'pm';
                    },

                    //Uppercase Ante meridiem and Post meridiem
                    A: function () {
                        return this.getHours() < 12 ? 'AM' : 'PM';
                    },

                    //Swatch Internet time
                    B: function () {
                        return null;
                    },

                    //12-hour format of an hour without leading zeros
                    g: function () {
                        var hours = this.getHours();
                        return hours > 12 ? hours - 12 : hours;
                    },

                    //24-hour format of an hour without leading zeros
                    G: function () {
                        return this.getHours();
                    },

                    //12-hour format of an hour with leading zeros
                    h: function () {
                        var hours = pattern['g'].call(this);
                        return hours < 10 ? '0' + hours : hours;
                    },

                    //24-hour format of an hour with leading zeros
                    H: function () {
                        var hours = pattern['G'].call(this);
                        return hours < 10 ? '0' + hours : hours;
                    },

                    //Minutes with leading zeros
                    i: function () {
                        return this.getMinutes() < 10 ? '0' + this.getMinutes() : this.getMinutes();
                    },

                    //Seconds, with leading zeros
                    s: function () {
                        return this.getSeconds() < 10 ? '0' + this.getSeconds() : this.getSeconds();;
                    },

                    //Microseconds
                    u: function () {
                        return this.getMilliseconds();
                    },

                    //Timezone identifier
                    e: function () {
                        return null;
                    },

                    //Whether or not the date is in daylight saving time
                    I: function () {
                        return null;
                    },

                    //Difference to Greenwich time (GMT) in hours
                    O: function () {
                        var offset = this.getTimezoneOffset() / 60;
                        return (offset < 0 ? '' : '+') + (offset < 10 ? '0' + offset : offset) + '00';
                    },

                    //Difference to Greenwich time (GMT) with colon between hours and minutes
                    P: function () {
                        var offset = pattern['O'].call(this);
                        return offset.slice(0,3) + ':' + offset.slice(-2);
                    },

                    //Timezone abbreviation
                    T: function () {
                        return null;
                    },

                    //Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive
                    Z: function () {
                        return parseInt(pattern['O'].call(this)) * 60;
                    },

                    //ISO 8601 date
                    c: function () {
                        function pad(x) {
                            return x < 10 ? '0'+ x : x;
                        }

                        return this.getUTCFullYear() + '-'
                                + pad(this.getUTCMonth() + 1) + '-'
                                + pad(this.getUTCDate()) + 'T'
                                + pad(this.getUTCHours()) + ':'
                                + pad(this.getUTCMinutes()) + ':'
                                + pad(this.getUTCSeconds()) + 'Z';
                    },

                    //RFC 2822 formatted date
                    r: function () {
                        return this.toUTCString();
                    },

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

            return function(formatString) {
                var builder = '',
                    character = '';

                for (var i = 0; i <= formatString.length; i++) {
                    character = formatString.charAt(i);

                    if(pattern.hasOwnProperty(character)) {
                        builder += pattern[character].call(this).toString();
                    }
                    else {
                        builder += character;
                    }
                }

                return builder;
            }
        }());

    }