Namespace comb.date

    /**
     * Returns the number of days in the month of a date
     *
     * @example
     *
     *  comb.date.getDaysInMonth(new Date(2006, 1, 1)) => 28
     *  comb.date.getDaysInMonth(new Date(2004, 1, 1)) => 29
     *  comb.date.getDaysInMonth(new Date(2006, 2, 1)) => 31
     *  comb.date.getDaysInMonth(new Date(2006, 3, 1)) => 30
     *  comb.date.getDaysInMonth(new Date(2006, 4, 1)) => 31
     *  comb.date.getDaysInMonth(new Date(2006, 5, 1)) => 30
     *  comb.date.getDaysInMonth(new Date(2006, 6, 1)) => 31
     * @param {Date} dateObject the date containing the month
     * @return {Number} the number of days in the month
     */
    getDaysInMonth:function (dateObject) {
        
        
        var month = dateObject.getMonth();
        var days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
        if (month == 1 && date.isLeapYear(dateObject)) {
            return 29;
        } 
        return days[month]; 
    },    /**
     * Determines if a date is a leap year
     *
     * @example
     *
     *  comb.date.isLeapYear(new Date(1600, 0, 1)) => true
     *  comb.date.isLeapYear(new Date(2004, 0, 1)) => true
     *  comb.date.isLeapYear(new Date(2000, 0, 1)) => true
     *  comb.date.isLeapYear(new Date(2006, 0, 1)) => false
     *  comb.date.isLeapYear(new Date(1900, 0, 1)) => false
     *  comb.date.isLeapYear(new Date(1800, 0, 1)) => false
     *  comb.date.isLeapYear(new Date(1700, 0, 1)) => false
     *
     * @param {Date} dateObject
     * @returns {Boolean} true if it is a leap year false otherwise
     */
    isLeapYear:function (dateObject, utc) {
        var year = dateObject[utc ? "getUTCFullYear" : "getFullYear"]();
        return !(year % 400) || (!(year % 4) && !!(year % 100)); 
    },    /**
     * Determines if a date is on a weekend
     *
     * @example
     *
     * var thursday = new Date(2006, 8, 21);
     * var saturday = new Date(2006, 8, 23);
     * var sunday = new Date(2006, 8, 24);
     * var monday = new Date(2006, 8, 25);
     * comb.date.isWeekend(thursday)) => false
     * comb.date.isWeekend(saturday) => true
     * comb.date.isWeekend(sunday) => true
     * comb.date.isWeekend(monday)) => false
     *
     * @param {Date} dateObject the date to test
     *
     * @returns {Boolean} true if the date is a weekend
     */
    isWeekend:function (dateObject, utc) {
        
        
        var day = (dateObject || new Date())[utc ? "getUTCDay" : "getDay"]();
        return day == 0 || day == 6;
    },    /**
     * Get the timezone of a date
     *
     * @example
     *  //just setting the strLocal to simulate the toString() of a date
     *  dt.str = 'Sun Sep 17 2006 22:25:51 GMT-0500 (CDT)';
     *  //just setting the strLocal to simulate the locale
     *  dt.strLocale = 'Sun 17 Sep 2006 10:25:51 PM CDT';
     *  comb.date.getTimezoneName(dt) => 'CDT'
     *  dt.str = 'Sun Sep 17 2006 22:57:18 GMT-0500 (CDT)';
     *  dt.strLocale = 'Sun Sep 17 22:57:18 2006';
     *  comb.date.getTimezoneName(dt) => 'CDT'
     * @param dateObject the date to get the timezone from
     *
     * @returns {String} the timezone of the date
     */
    getTimezoneName:function (dateObject) {
        var str = dateObject.toString();
        var tz = '';
        var pos = str.indexOf('(');
        if (pos > -1) {
            tz = str.substring(++pos, str.indexOf(')'));
        }
        return tz; 
    },
    /**
     * Compares two dates
     *
     * @example
     *
     * var d1 = new Date();
     * d1.setHours(0);
     * comb.date.compare(d1, d1) => 0
     *
     *  var d1 = new Date();
     *  d1.setHours(0);
     *  var d2 = new Date();
     *  d2.setFullYear(2005);
     *  d2.setHours(12);
     *  comb.date.compare(d1, d2, "date") => 1
     *  comb.date.compare(d1, d2, "datetime") => 1
     *
     *  var d1 = new Date();
     *  d1.setHours(0);
     *  var d2 = new Date();
     *  d2.setFullYear(2005);
     *  d2.setHours(12);
     *  comb.date.compare(d2, d1, "date"), -1);
     *  comb.date.compare(d1, d2, "time"), -1);
     *
     * @param {Date|String} date1 the date to comapare
     * @param {Date|String} [date2=new Date()] the date to compare date1 againse
     * @param {"date"|"time"|"datetime"} portion compares the portion specified
     *
     * @returns -1 if date1 is < date2 0 if date1 === date2  1 if date1 > date2
     */
    compare:function (date1, date2, portion) {
        date1 = new Date(date1);
        date2 = new Date((date2 || new Date()));        if (portion == "date") {
            
            date1.setHours(0, 0, 0, 0);
            date2.setHours(0, 0, 0, 0);
        } else if (portion == "time") {
            
            date1.setFullYear(0, 0, 0);
            date2.setFullYear(0, 0, 0);
        }
        var ret = 0;
        date1 > date2 && (ret = 1);
        date1 < date2 && (ret = -1);
        return ret; 
    },
    /**
     * Adds a specified interval and amount to a date
     *
     * @example
     *  var dtA = new Date(2005, 11, 27);
     *  comb.date.add(dtA, "year", 1) => new Date(2006, 11, 27);
     *  comb.date.add(dtA, "years", 1) => new Date(2006, 11, 27);
     *
     *  dtA = new Date(2000, 0, 1);
     *  comb.date.add(dtA, "quarter", 1) => new Date(2000, 3, 1);
     *  comb.date.add(dtA, "quarters", 1) => new Date(2000, 3, 1);
     *
     *  dtA = new Date(2000, 0, 1);
     *  comb.date.add(dtA, "month", 1) => new Date(2000, 1, 1);
     *  comb.date.add(dtA, "months", 1) => new Date(2000, 1, 1);
     *
     *  dtA = new Date(2000, 0, 31);
     *  comb.date.add(dtA, "month", 1) => new Date(2000, 1, 29);
     *  comb.date.add(dtA, "months", 1) => new Date(2000, 1, 29);
     *
     *  dtA = new Date(2000, 0, 1);
     *  comb.date.add(dtA, "week", 1) => new Date(2000, 0, 8);
     *  comb.date.add(dtA, "weeks", 1) => new Date(2000, 0, 8);
     *
     *  dtA = new Date(2000, 0, 1);
     *  comb.date.add(dtA, "day", 1) => new Date(2000, 0, 2);
     *
     *  dtA = new Date(2000, 0, 1);
     *  comb.date.add(dtA, "weekday", 1) => new Date(2000, 0, 3);
     *
     *  dtA = new Date(2000, 0, 1, 11);
     *  comb.date.add(dtA, "hour", 1) => new Date(2000, 0, 1, 12);
     *
     *  dtA = new Date(2000, 11, 31, 23, 59);
     *  comb.date.add(dtA, "minute", 1) => new Date(2001, 0, 1, 0, 0);
     *
     *  dtA = new Date(2000, 11, 31, 23, 59, 59);
     *  comb.date.add(dtA, "second", 1) => new Date(2001, 0, 1, 0, 0, 0);
     *
     *  dtA = new Date(2000, 11, 31, 23, 59, 59, 999);
     *  comb.date.add(dtA, "millisecond", 1) => new Date(2001, 0, 1, 0, 0, 0, 0);
     *
     * @param {Date} date
     * @param {String} interval the interval to add
     *  <ul>
     *      <li>day | days</li>
     *      <li>weekday | weekdays</li>
     *      <li>year | years</li>
     *      <li>week | weeks</li>
     *      <li>quarter | quarters</li>
     *      <li>months | months</li>
     *      <li>hour | hours</li>
     *      <li>minute | minutes</li>
     *      <li>second | seconds</li>
     *      <li>millisecond | milliseconds</li>
     *  </ul>
     * @param {Number} [amount=0] the amount to add
     */
    add:function (date, interval, amount) {
        amount = amount | 0
        var sum = new Date(date);
        var fixOvershoot = false;
        var property = "Date";        
        switch (interval) {
            case "day":
            case "days" :
                break;
            case "weekday":
            case "weekdays":
                
                
                
                
                var days, weeks, mod = amount % 5, strt = date.getDay(), adj = 0;
                if (!mod) {
                    days = (amount > 0) ? 5 : -5;
                    weeks = (amount > 0) ? ((amount - 5) / 5) : ((amount + 5) / 5);
                } else {
                    days = mod;
                    weeks = parseInt(amount / 5);
                }
                if (strt == 6 && amount > 0) {
                    adj = 1;
                } else if (strt == 0 && amount < 0) {
                    
                    
                    adj = -1;
                }
                
                var trgt = strt + days;
                
                if (trgt == 0 || trgt == 6) {
                    adj = (amount > 0) ? 2 : -2;
                }
                
                
                amount = (7 * weeks) + days + adj;
                break;
            case "year":
            case "years":
                property = "FullYear";
                fixOvershoot = true;
                break;
            case "week":
            case "weeks":
                amount *= 7;
                break;
            case "quarter":
            case "quarters" :
                
                amount *= 3;
            case "month":
            case "months":
                
                fixOvershoot = true;
                property = "Month";
                break;
            default:
                interval = interval.replace(/s$/, "");
                property = "UTC" + interval.charAt(0).toUpperCase() + interval.substring(1) + "s";
        }        if (property) {
            sum["set" + property](sum["get" + property]() + amount);
        }        if (fixOvershoot && (sum.getDate() < date.getDate())) {
            sum.setDate(0);
        }        return sum; 
    },    /**
     * Finds the difference between two dates based on the specified interval
     *
     * @example
     *
     * var dtA, dtB;
     *
     * dtA = new Date(2005, 11, 27);
     * dtB = new Date(2006, 11, 27);
     * comb.date.difference(dtA, dtB, "year") => 1
     *
     * dtA = new Date(2000, 1, 29);
     * dtB = new Date(2001, 2, 1);
     * comb.date.difference(dtA, dtB, "quarter") => 4
     * comb.date.difference(dtA, dtB, "month") => 13
     *
     * dtA = new Date(2000, 1, 1);
     * dtB = new Date(2000, 1, 8);
     * comb.date.difference(dtA, dtB, "week") => 1
     *
     * dtA = new Date(2000, 1, 29);
     * dtB = new Date(2000, 2, 1);
     * comb.date.difference(dtA, dtB, "day") => 1
     *
     * dtA = new Date(2006, 7, 3);
     * dtB = new Date(2006, 7, 11);
     * comb.date.difference(dtA, dtB, "weekday") => 6
     *
     * dtA = new Date(2000, 11, 31, 23);
     * dtB = new Date(2001, 0, 1, 0);
     * comb.date.difference(dtA, dtB, "hour") => 1
     *
     * dtA = new Date(2000, 11, 31, 23, 59);
     * dtB = new Date(2001, 0, 1, 0, 0);
     * comb.date.difference(dtA, dtB, "minute") => 1
     *
     * dtA = new Date(2000, 11, 31, 23, 59, 59);
     * dtB = new Date(2001, 0, 1, 0, 0, 0);
     * comb.date.difference(dtA, dtB, "second") => 1
     *
     * dtA = new Date(2000, 11, 31, 23, 59, 59, 999);
     * dtB = new Date(2001, 0, 1, 0, 0, 0, 0);
     * comb.date.difference(dtA, dtB, "millisecond") => 1
     *
     *
     * @param {Date} date1
     * @param {Date} [date2 = new Date()]
     * @param {String} [interval = "day"] the intercal to find the difference of.
     *   <ul>
     *      <li>day | days</li>
     *      <li>weekday | weekdays</li>
     *      <li>year | years</li>
     *      <li>week | weeks</li>
     *      <li>quarter | quarters</li>
     *      <li>months | months</li>
     *      <li>hour | hours</li>
     *      <li>minute | minutes</li>
     *      <li>second | seconds</li>
     *      <li>millisecond | milliseconds</li>
     *  </ul>
     */
    difference:function (date1, date2, interval, utc) {
        date2 = date2 || new Date();
        interval = interval || "day";
        var yearDiff = date2.getFullYear() - date1.getFullYear();
        var delta = 1;         switch (interval) {
            case "quarter":
            case "quarters":
                var m1 = date1[utc ? "getUTCMonth" : "getMonth"]();
                var m2 = date2[utc ? "getUTCMonth" : "getMonth"]();
                
                var q1 = floor(m1 / 3) + 1;
                var q2 = floor(m2 / 3) + 1;
                
                q2 += (yearDiff * 4);
                delta = q2 - q1;
                break;
            case "weekday":
            case "weekdays":
                var days = round(date.difference(date1, date2, "day", utc));
                var weeks = parseInt(date.difference(date1, date2, "week", utc));
                var mod = days % 7;                
                if (mod == 0) {
                    days = weeks * 5;
                } else {
                    
                    var adj = 0;
                    var aDay = date1[utc ? "getUTCDay" : "getDay"]();
                    var bDay = date2[utc ? "getUTCDay" : "getDay"]();                    weeks = parseInt(days / 7);
                    mod = days % 7;
                    
                    
                    var dtMark = new Date(date1);
                    dtMark.setDate(dtMark[utc ? "getUTCDate" : "getDate"]() + (weeks * 7));
                    var dayMark = dtMark[utc ? "getUTCDay" : "getDay"]();                    
                    if (days > 0) {
                        switch (true) {
                            
                            case (aDay == 6 || bDay == 6):
                                adj = -1;
                                break;
                            
                            case aDay == 0:
                                adj = 0;
                                break;
                            
                            case bDay == 0:
                                adj = -2;
                                break;
                            
                            case (dayMark + mod) > 5:
                                adj = -2;
                        }
                    } else if (days < 0) {
                        switch (true) {
                            
                            case aDay == 6:
                                adj = 0;
                                break;
                            
                            case aDay == 0:
                                adj = 1;
                                break;
                            
                            case bDay == 6:
                                adj = 2;
                                break;
                            
                            case bDay == 0:
                                adj = 1;
                                break;
                            
                            case (dayMark + mod) < 0:
                                adj = 2;
                        }
                    }
                    days += adj;
                    days -= (weeks * 2);
                }
                delta = days;
                break;
            case "year":
            case "years":
                delta = yearDiff;
                break;
            case "month":
            case "months":
                var m1 = date1[utc ? "getUTCMonth" : "getMonth"]();
                var m2 = date2[utc ? "getUTCMonth" : "getMonth"]();
                delta = (m2 - m1) + (yearDiff * 12);
                break;
            case "week":
            case "weeks":
                delta = parseInt(date.difference(date1, date2, "day", utc) / 7);
                break;
            case "day":
            case "days":
                delta /= 24;
            case "hour":
            case "hours":
                delta /= 60;
            case "minute":
            case "minutes":
                delta /= 60;
            case "second":
            case "seconds":
                delta /= 1000;
            case "millisecond":
            case "milliseconds":
                delta *= date2.getTime() - date1.getTime();
        }        
        return round(delta); 
    },
    /**
     * Parses a date string into a date object
     *
     * @example
     *  var aug_11_2006 = new Date(2006, 7, 11, 0);
     *  comb.date.parse("08/11/06", "MM/dd/yy") => aug_11_2006
     *  comb.date.parse("11Aug2006", 'ddMMMyyyy') => aug_11_2006
     *  comb.date.parse("Aug2006", 'MMMyyyy') => new Date(2006, 7, 1)
     *  comb.date.parse("Aug 11, 2006", "MMM dd, yyyy") => aug_11_2006
     *  comb.date.parse("August 11, 2006", "MMMM dd, yyyy") => aug_11_2006
     *  comb.date.parse("Friday, August 11, 2006", "EEEE, MMMM dd, yyyy") => aug_11_2006
     *
     * @param {String} dateStr The string to parse
     * @param {String} format the format of the date composed of the following options
     * <ul>
     *                  <li> G    Era designator    Text    AD</li>
     *                  <li> y    Year    Year    1996; 96</li>
     *                  <li> M    Month in year    Month    July; Jul; 07</li>
     *                  <li> w    Week in year    Number    27</li>
     *                  <li> W    Week in month    Number    2</li>
     *                  <li> D    Day in year    Number    189</li>
     *                  <li> d    Day in month    Number    10</li>
     *                  <li> E    Day in week    Text    Tuesday; Tue</li>
     *                  <li> a    Am/pm marker    Text    PM</li>
     *                  <li> H    Hour in day (0-23)    Number    0</li>
     *                  <li> k    Hour in day (1-24)    Number    24</li>
     *                  <li> K    Hour in am/pm (0-11)    Number    0</li>
     *                  <li> h    Hour in am/pm (1-12)    Number    12</li>
     *                  <li> m    Minute in hour    Number    30</li>
     *                  <li> s    Second in minute    Number    55</li>
     *                  <li> S    Millisecond    Number    978</li>
     *                  <li> z    Time zone    General time zone    Pacific Standard Time; PST; GMT-08:00</li>
     *                  <li> Z    Time zone    RFC 822 time zone    -0800 </li>
     * </ul>
     *
     * @returns {Date} the parsed date
     *
     *
     */
    parse:function (dateStr, format) {
        if (!format) throw new Error('format required when calling comb.date.parse');
        var tokens = [], regexp = buildDateEXP(format, tokens),
            re = new RegExp("^" + regexp + "$", "i"),
            match = re.exec(dateStr);
        if (!match) {
            return null;
        } 
        var result = [1970, 0, 1, 0, 0, 0, 0], 
            amPm = "",
            valid = match.every(function (v, i) {
                if (!i) {
                    return true;
                }
                var token = tokens[i - 1];
                var l = token.length;
                switch (token.charAt(0)) {
                    case 'y':
                        if (v < 100) {
                            v = parseInt(v, 10);
                            
                            
                            var year = '' + new Date().getFullYear(),
                                century = year.substring(0, 2) * 100,
                                cutoff = min(year.substring(2, 4) + 20, 99);
                            result[0] = (v < cutoff) ? century + v : century - 100 + v;
                        } else {
                            result[0] = v;
                        }
                        break;
                    case 'M':
                        if (l > 2) {
                            var months = monthNames;
                            if (l === 3) {
                                months = monthAbbr;
                            }
                            
                            
                            v = v.replace(".", "").toLowerCase();
                            months = months.map(function (s) {
                                return s.replace(".", "").toLowerCase();
                            });
                            if ((v = months.indexOf(v)) == -1) {
                                return false;
                            }
                        } else {
                            v--;
                        }
                        result[1] = v;
                        break;
                    case 'E':
                    case 'e':
                        var days = dayNames;
                        if (l == 3) {
                            days = dayAbbr;
                        }
                        
                        v = v.toLowerCase();
                        days = days.map(function (d) {
                            return d.toLowerCase();
                        });
                        var d = days.indexOf(v);
                        if (d == -1) {
                            v = parseInt(v);
                            if (isNaN(v) || v > days.length) {
                                return false;
                            }
                        } else {
                            v = d;
                        }
                        break;
                    case 'D':
                        result[1] = 0;
                    case 'd':
                        result[2] = v;
                        break;
                    case 'a': 
                        var am = "am";
                        var pm = "pm";
                        var period = /\./g;
                        v = v.replace(period, '').toLowerCase();
                        
                        amPm = (v == pm) ? 'p' : (v == am) ? 'a' : '';
                        break;
                    case 'k': 
                        if (v == 24) {
                            v = 0;
                        }
                    
                    case 'h': 
                    case 'H': 
                    case 'K': 
                        
                        
                        result[3] = v;
                        break;
                    case 'm': 
                        result[4] = v;
                        break;
                    case 's': 
                        result[5] = v;
                        break;
                    case 'S': 
                        result[6] = v;
                        break;
                }
                return true;
            });
        if (valid) {
            var hours = +result[3];
            
            if (amPm === 'p' && hours < 12) {
                result[3] = hours + 12; 
            } else if (amPm === 'a' && hours == 12) {
                result[3] = 0; 
            }
            var dateObject = new Date(result[0], result[1], result[2], result[3], result[4], result[5], result[6]); 
            var dateToken = (tokens.indexOf('d') != -1),
                monthToken = (tokens.indexOf('M') != -1),
                month = result[1],
                day = result[2],
                dateMonth = dateObject.getMonth(),
                dateDay = dateObject.getDate();
            if ((monthToken && dateMonth > month) || (dateToken && dateDay > day)) {
                return null;
            }
            return dateObject; 
        } else {
            return null;
        }
    },    /**
     * Formats a date to the specidifed format string
     *
     * @example
     *
     * var date = new Date(2006, 7, 11, 0, 55, 12, 345);
     * comb.date.format(date, "EEEE, MMMM dd, yyyy") => "Friday, August 11, 2006"
     * comb.date.format(date, "M/dd/yy") => "8/11/06"
     * comb.date.format(date, "E") => "6"
     * comb.date.format(date, "h:m a") => "12:55 AM"
     * comb.date.format(date, 'h:m:s') => "12:55:12"
     * comb.date.format(date, 'h:m:s.SS') => "12:55:12.35"
     * comb.date.format(date, 'k:m:s.SS') => "24:55:12.35"
     * comb.date.format(date, 'H:m:s.SS') => "0:55:12.35"
     * comb.date.format(date, "ddMMyyyy") => "11082006"
     *
     * @param date the date to format
     * @param {String} format the format of the date composed of the following options
     * <ul>
     *                  <li> G    Era designator    Text    AD</li>
     *                  <li> y    Year    Year    1996; 96</li>
     *                  <li> M    Month in year    Month    July; Jul; 07</li>
     *                  <li> w    Week in year    Number    27</li>
     *                  <li> W    Week in month    Number    2</li>
     *                  <li> D    Day in year    Number    189</li>
     *                  <li> d    Day in month    Number    10</li>
     *                  <li> E    Day in week    Text    Tuesday; Tue</li>
     *                  <li> a    Am/pm marker    Text    PM</li>
     *                  <li> H    Hour in day (0-23)    Number    0</li>
     *                  <li> k    Hour in day (1-24)    Number    24</li>
     *                  <li> K    Hour in am/pm (0-11)    Number    0</li>
     *                  <li> h    Hour in am/pm (1-12)    Number    12</li>
     *                  <li> m    Minute in hour    Number    30</li>
     *                  <li> s    Second in minute    Number    55</li>
     *                  <li> S    Millisecond    Number    978</li>
     *                  <li> z    Time zone    General time zone    Pacific Standard Time; PST; GMT-08:00</li>
     *                  <li> Z    Time zone    RFC 822 time zone    -0800 </li>
     * </ul>
     */
    format:function (date, format, utc) {
        utc = utc || false;
        var fullYear, month, day, d, hour, minute, second, millisecond;
        if (utc) {
            fullYear = date.getUTCFullYear(),
                month = date.getUTCMonth(),
                day = date.getUTCDay(),
                d = date.getUTCDate(),
                hour = date.getUTCHours(),
                minute = date.getUTCMinutes(),
                second = date.getUTCSeconds(),
                millisecond = date.getUTCMilliseconds();
        } else {
            fullYear = date.getFullYear(),
                month = date.getMonth(),
                d = date.getDate(),
                day = date.getDay(),
                hour = date.getHours(),
                minute = date.getMinutes(),
                second = date.getSeconds(),
                millisecond = date.getMilliseconds();
        }
        return format.replace(/([a-z])\1*/ig, function (match, options) {
            var s, pad, h,
                c = match.charAt(0),
                l = match.length;            switch (c) {
                case 'd':
                    s = "" + d;
                case 'H':
                    !s && (s = "" + hour);
                case 'm':
                    !s && (s = "" + minute);
                case 's':
                    !s && (s = "" + second);
                    pad = true;
                    break;
                case 'G':
                    s = ((l < 4) ? eraAbbr : eraNames)[fullYear < 0 ? 0 : 1];
                    break;
                case 'y':
                    s = fullYear;
                    if (l > 1) {
                        l == 2 ? s = string.truncate("" + s, 2, true) : pad = true;
                    }
                    break;
                case 'Q':
                case 'q':
                    s = ceil((month + 1) / 3);
                    pad = true;
                    break;
                case 'M':
                    if (l < 3) {
                        s = month + 1;
                        pad = true;
                    } else {
                        s = (l == 3 ? monthAbbr : monthNames)[month];
                    }
                    break;
                case 'w':
                    s = getWeekOfYear(date, 0, utc), pad = true;
                    break;
                case 'D':
                    s = getDayOfYear(date, utc), pad = true;
                    break;
                case 'E':
                    if (l < 3) {
                        s = day + 1;
                        pad = true;
                    } else {
                        s = (l == 3 ? dayAbbr : dayNames)[day];
                    }
                    break;
                case 'a':
                    s = (hour < 12) ? 'AM' : 'PM';
                    break;
                case 'h':
                    s = (hour % 12) || 12, pad = true;
                    break;
                case 'K':
                    s = (hour % 12), pad = true;
                    break;
                case 'k':
                    s = hour || 24, pad = true;
                    break;
                case 'S':
                    s = round(millisecond * pow(10, l - 3)), pad = true;
                    break;
                case 'v':
                case 'z':
                    s = comb.date.getTimezoneName(date);
                    if (s) {
                        break;
                    }
                    l = 4;
                
                case 'Z':
                    var offset = date.getTimezoneOffset();
                    var tz = [
                        (offset >= 0 ? "-" : "+"),
                        string.pad(floor(abs(offset) / 60), 2, "0"),
                        string.pad(abs(offset) % 60, 2, "0")
                    ];
                    if (l == 4) {
                        tz.splice(0, 0, "GMT");
                        tz.splice(3, 0, ":");
                    }
                    s = tz.join("");
                    break;


                default:
                    s = match;
                
            }
            if (pad) {
                s = string.pad(s, l, '0');
            }
            return s;
        });
    }

amount = amount | 0
var sum = new Date(date);
var fixOvershoot = false;
var property = "Date";


switch (interval) {
    case "day":
    case "days" :
        break;
    case "weekday":
    case "weekdays":
        
        
        
        
        var days, weeks, mod = amount % 5, strt = date.getDay(), adj = 0;
        if (!mod) {
            days = (amount > 0) ? 5 : -5;
            weeks = (amount > 0) ? ((amount - 5) / 5) : ((amount + 5) / 5);
        } else {
            days = mod;
            weeks = parseInt(amount / 5);
        }
        if (strt == 6 && amount > 0) {
            adj = 1;
        } else if (strt == 0 && amount < 0) {
            
            
            adj = -1;
        }
        
        var trgt = strt + days;
        
        if (trgt == 0 || trgt == 6) {
            adj = (amount > 0) ? 2 : -2;
        }
        
        
        amount = (7 * weeks) + days + adj;
        break;
    case "year":
    case "years":
        property = "FullYear";
        fixOvershoot = true;
        break;
    case "week":
    case "weeks":
        amount *= 7;
        break;
    case "quarter":
    case "quarters" :
        
        amount *= 3;
    case "month":
    case "months":
        
        fixOvershoot = true;
        property = "Month";
        break;
    default:
        interval = interval.replace(/s$/, "");
        property = "UTC" + interval.charAt(0).toUpperCase() + interval.substring(1) + "s";
}

if (property) {
    sum["set" + property](sum["get" + property]() + amount);
}

if (fixOvershoot && (sum.getDate() < date.getDate())) {
    sum.setDate(0);
}

return sum; 
    

date1 = new Date(date1);
date2 = new Date((date2 || new Date()));

if (portion == "date") {
    
    date1.setHours(0, 0, 0, 0);
    date2.setHours(0, 0, 0, 0);
} else if (portion == "time") {
    
    date1.setFullYear(0, 0, 0);
    date2.setFullYear(0, 0, 0);
}
var ret = 0;
date1 > date2 && (ret = 1);
date1 < date2 && (ret = -1);
return ret; 
    

date2 = date2 || new Date();
interval = interval || "day";
var yearDiff = date2.getFullYear() - date1.getFullYear();
var delta = 1; 

switch (interval) {
    case "quarter":
    case "quarters":
        var m1 = date1[utc ? "getUTCMonth" : "getMonth"]();
        var m2 = date2[utc ? "getUTCMonth" : "getMonth"]();
        
        var q1 = floor(m1 / 3) + 1;
        var q2 = floor(m2 / 3) + 1;
        
        q2 += (yearDiff * 4);
        delta = q2 - q1;
        break;
    case "weekday":
    case "weekdays":
        var days = round(date.difference(date1, date2, "day", utc));
        var weeks = parseInt(date.difference(date1, date2, "week", utc));
        var mod = days % 7;

        
        if (mod == 0) {
            days = weeks * 5;
        } else {
            
            var adj = 0;
            var aDay = date1[utc ? "getUTCDay" : "getDay"]();
            var bDay = date2[utc ? "getUTCDay" : "getDay"]();

            weeks = parseInt(days / 7);
            mod = days % 7;
            
            
            var dtMark = new Date(date1);
            dtMark.setDate(dtMark[utc ? "getUTCDate" : "getDate"]() + (weeks * 7));
            var dayMark = dtMark[utc ? "getUTCDay" : "getDay"]();

            
            if (days > 0) {
                switch (true) {
                    
                    case (aDay == 6 || bDay == 6):
                        adj = -1;
                        break;
                    
                    case aDay == 0:
                        adj = 0;
                        break;
                    
                    case bDay == 0:
                        adj = -2;
                        break;
                    
                    case (dayMark + mod) > 5:
                        adj = -2;
                }
            } else if (days < 0) {
                switch (true) {
                    
                    case aDay == 6:
                        adj = 0;
                        break;
                    
                    case aDay == 0:
                        adj = 1;
                        break;
                    
                    case bDay == 6:
                        adj = 2;
                        break;
                    
                    case bDay == 0:
                        adj = 1;
                        break;
                    
                    case (dayMark + mod) < 0:
                        adj = 2;
                }
            }
            days += adj;
            days -= (weeks * 2);
        }
        delta = days;
        break;
    case "year":
    case "years":
        delta = yearDiff;
        break;
    case "month":
    case "months":
        var m1 = date1[utc ? "getUTCMonth" : "getMonth"]();
        var m2 = date2[utc ? "getUTCMonth" : "getMonth"]();
        delta = (m2 - m1) + (yearDiff * 12);
        break;
    case "week":
    case "weeks":
        delta = parseInt(date.difference(date1, date2, "day", utc) / 7);
        break;
    case "day":
    case "days":
        delta /= 24;
    case "hour":
    case "hours":
        delta /= 60;
    case "minute":
    case "minutes":
        delta /= 60;
    case "second":
    case "seconds":
        delta /= 1000;
    case "millisecond":
    case "milliseconds":
        delta *= date2.getTime() - date1.getTime();
}


return round(delta); 
    

utc = utc || false;
var fullYear, month, day, d, hour, minute, second, millisecond;
if (utc) {
    fullYear = date.getUTCFullYear(),
        month = date.getUTCMonth(),
        day = date.getUTCDay(),
        d = date.getUTCDate(),
        hour = date.getUTCHours(),
        minute = date.getUTCMinutes(),
        second = date.getUTCSeconds(),
        millisecond = date.getUTCMilliseconds();
} else {
    fullYear = date.getFullYear(),
        month = date.getMonth(),
        d = date.getDate(),
        day = date.getDay(),
        hour = date.getHours(),
        minute = date.getMinutes(),
        second = date.getSeconds(),
        millisecond = date.getMilliseconds();
}
return format.replace(/([a-z])\1*/ig, function (match, options) {
    var s, pad, h,
        c = match.charAt(0),
        l = match.length;

    switch (c) {
        case 'd':
            s = "" + d;
        case 'H':
            !s && (s = "" + hour);
        case 'm':
            !s && (s = "" + minute);
        case 's':
            !s && (s = "" + second);
            pad = true;
            break;
        case 'G':
            s = ((l < 4) ? eraAbbr : eraNames)[fullYear < 0 ? 0 : 1];
            break;
        case 'y':
            s = fullYear;
            if (l > 1) {
                l == 2 ? s = string.truncate("" + s, 2, true) : pad = true;
            }
            break;
        case 'Q':
        case 'q':
            s = ceil((month + 1) / 3);
            pad = true;
            break;
        case 'M':
            if (l < 3) {
                s = month + 1;
                pad = true;
            } else {
                s = (l == 3 ? monthAbbr : monthNames)[month];
            }
            break;
        case 'w':
            s = getWeekOfYear(date, 0, utc), pad = true;
            break;
        case 'D':
            s = getDayOfYear(date, utc), pad = true;
            break;
        case 'E':
            if (l < 3) {
                s = day + 1;
                pad = true;
            } else {
                s = (l == 3 ? dayAbbr : dayNames)[day];
            }
            break;
        case 'a':
            s = (hour < 12) ? 'AM' : 'PM';
            break;
        case 'h':
            s = (hour % 12) || 12, pad = true;
            break;
        case 'K':
            s = (hour % 12), pad = true;
            break;
        case 'k':
            s = hour || 24, pad = true;
            break;
        case 'S':
            s = round(millisecond * pow(10, l - 3)), pad = true;
            break;
        case 'v':
        case 'z':
            s = comb.date.getTimezoneName(date);
            if (s) {
                break;
            }
            l = 4;
        
        case 'Z':
            var offset = date.getTimezoneOffset();
            var tz = [
                (offset >= 0 ? "-" : "+"),
                string.pad(floor(abs(offset) / 60), 2, "0"),
                string.pad(abs(offset) % 60, 2, "0")
            ];
            if (l == 4) {
                tz.splice(0, 0, "GMT");
                tz.splice(3, 0, ":");
            }
            s = tz.join("");
            break;


        default:
            s = match;
        
    }
    if (pad) {
        s = string.pad(s, l, '0');
    }
    return s;
});
    

var month = dateObject.getMonth();
var days = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
if (month == 1 && date.isLeapYear(dateObject)) {
    return 29;
} 
return days[month]; 
    

var str = dateObject.toString();
var tz = '';
var pos = str.indexOf('(');
if (pos > -1) {
    tz = str.substring(++pos, str.indexOf(')'));
}
return tz; 
    

var year = dateObject[utc ? "getUTCFullYear" : "getFullYear"]();
return !(year % 400) || (!(year % 4) && !!(year % 100)); 
    

var day = (dateObject || new Date())[utc ? "getUTCDay" : "getDay"]();
return day == 0 || day == 6;
    

if (!format) throw new Error('format required when calling comb.date.parse');
var tokens = [], regexp = buildDateEXP(format, tokens),
    re = new RegExp("^" + regexp + "$", "i"),
    match = re.exec(dateStr);
if (!match) {
    return null;
} 
var result = [1970, 0, 1, 0, 0, 0, 0], 
    amPm = "",
    valid = match.every(function (v, i) {
        if (!i) {
            return true;
        }
        var token = tokens[i - 1];
        var l = token.length;
        switch (token.charAt(0)) {
            case 'y':
                if (v < 100) {
                    v = parseInt(v, 10);
                    
                    
                    var year = '' + new Date().getFullYear(),
                        century = year.substring(0, 2) * 100,
                        cutoff = min(year.substring(2, 4) + 20, 99);
                    result[0] = (v < cutoff) ? century + v : century - 100 + v;
                } else {
                    result[0] = v;
                }
                break;
            case 'M':
                if (l > 2) {
                    var months = monthNames;
                    if (l === 3) {
                        months = monthAbbr;
                    }
                    
                    
                    v = v.replace(".", "").toLowerCase();
                    months = months.map(function (s) {
                        return s.replace(".", "").toLowerCase();
                    });
                    if ((v = months.indexOf(v)) == -1) {
                        return false;
                    }
                } else {
                    v--;
                }
                result[1] = v;
                break;
            case 'E':
            case 'e':
                var days = dayNames;
                if (l == 3) {
                    days = dayAbbr;
                }
                
                v = v.toLowerCase();
                days = days.map(function (d) {
                    return d.toLowerCase();
                });
                var d = days.indexOf(v);
                if (d == -1) {
                    v = parseInt(v);
                    if (isNaN(v) || v > days.length) {
                        return false;
                    }
                } else {
                    v = d;
                }
                break;
            case 'D':
                result[1] = 0;
            case 'd':
                result[2] = v;
                break;
            case 'a': 
                var am = "am";
                var pm = "pm";
                var period = /\./g;
                v = v.replace(period, '').toLowerCase();
                
                amPm = (v == pm) ? 'p' : (v == am) ? 'a' : '';
                break;
            case 'k': 
                if (v == 24) {
                    v = 0;
                }
            
            case 'h': 
            case 'H': 
            case 'K': 
                
                
                result[3] = v;
                break;
            case 'm': 
                result[4] = v;
                break;
            case 's': 
                result[5] = v;
                break;
            case 'S': 
                result[6] = v;
                break;
        }
        return true;
    });
if (valid) {
    var hours = +result[3];
    
    if (amPm === 'p' && hours < 12) {
        result[3] = hours + 12; 
    } else if (amPm === 'a' && hours == 12) {
        result[3] = 0; 
    }
    var dateObject = new Date(result[0], result[1], result[2], result[3], result[4], result[5], result[6]); 
    var dateToken = (tokens.indexOf('d') != -1),
        monthToken = (tokens.indexOf('M') != -1),
        month = result[1],
        day = result[2],
        dateMonth = dateObject.getMonth(),
        dateDay = dateObject.getDate();
    if ((monthToken && dateMonth > month) || (dateToken && dateDay > day)) {
        return null;
    }
    return dateObject; 
} else {
    return null;
}