calc.php

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    } // end func dateToDays

    /**
     * Converts number of days to a distant unspecified epoch.
     *
     * @param int number of days
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in specified format
     */

    function daysToDate($days,$format="%Y%m%d")
    {

        $days     -=   1721119;
        $century  =    floor(( 4 * $days -  1) /  146097);
        $days     =    floor(4 * $days - 1 - 146097 * $century);
        $day      =    floor($days /  4);

        $year     =    floor(( 4 * $day +  3) /  1461);
        $day      =    floor(4 * $day +  3 -  1461 * $year);
        $day      =    floor(($day +  4) /  4);

        $month    =    floor(( 5 * $day -  3) /  153);
        $day      =    floor(5 * $day -  3 -  153 * $month);
        $day      =    floor(($day +  5) /  5);

        if($month < 10)
            $month +=3;
        else
        {
            $month -=9;
            if($year++ == 99)
            {
                $year = 0;
                $century++;
            }
        }

        $century = sprintf("%02d",$century);
        $year = sprintf("%02d",$year);
        return(Date_Calc::dateFormat($day,$month,$century.$year,$format));

    } // end func daysToDate

    /**
     * Calculates the date of the Nth weekday of the month,
     * such as the second Saturday of January 2000.
     *
     * @param string occurance: 1=first, 2=second, 3=third, etc.
     * @param string dayOfWeek: 0=Sunday, 1=Monday, etc.
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    function NWeekdayOfMonth($occurance,$dayOfWeek,$month,$year,$format="%Y%m%d")
    {
        $year = sprintf("%04d",$year);
        $month = sprintf("%02d",$month);

        $DOW1day = sprintf("%02d",(($occurance - 1) * 7 + 1));
        $DOW1 = Date_Calc::dayOfWeek($DOW1day,$month,$year);

        $wdate = ($occurance - 1) * 7 + 1 +
                (7 + $dayOfWeek - $DOW1) % 7;

        if( $wdate > Date_Calc::daysInMonth($month,$year)) {
            return -1;
        } else {
            return(Date_Calc::dateFormat($wdate,$month,$year,$format));
        }

    } // end func NWeekdayOfMonth

    /**
     *  Formats the date in the given format, much like
     *  strfmt(). This function is used to alleviate the
     *  problem with 32-bit numbers for dates pre 1970
     *  or post 2038, as strfmt() has on most systems.
     *  Most of the formatting options are compatible.
     *
     *  formatting options:
     *
     *  %a        abbreviated weekday name (Sun, Mon, Tue)
     *  %A        full weekday name (Sunday, Monday, Tuesday)
     *  %b        abbreviated month name (Jan, Feb, Mar)
     *  %B        full month name (January, February, March)
     *  %d        day of month (range 00 to 31)
     *  %e        day of month, single digit (range 0 to 31)
     *  %E        number of days since unspecified epoch (integer)
     *             (%E is useful for passing a date in a URL as
     *             an integer value. Then simply use
     *             daysToDate() to convert back to a date.)
     *  %j        day of year (range 001 to 366)
     *  %m        month as decimal number (range 1 to 12)
     *  %n        newline character (\n)
     *  %t        tab character (\t)
     *  %w        weekday as decimal (0 = Sunday)
     *  %U        week number of current year, first sunday as first week
     *  %y        year as decimal (range 00 to 99)
     *  %Y        year as decimal including century (range 0000 to 9999)
     *  %%        literal '%'
     *
     * @param string year in format CCYY
     * @param string month in format MM
     * @param string day in format DD
     * @param string format for returned date
     *
     * @access public
     *
     * @return string date in given format
     */

    function dateFormat($day,$month,$year,$format)
    {
        if(!Date_Calc::isValidDate($day,$month,$year))
        {
            $year = Date_Calc::dateNow("%Y");
            $month = Date_Calc::dateNow("%m");
            $day = Date_Calc::dateNow("%d");
        }

        $output = "";

        for($strpos = 0; $strpos < strlen($format); $strpos++)
        {
            $char = substr($format,$strpos,1);
            if($char == "%")
            {
                $nextchar = substr($format,$strpos + 1,1);
                switch($nextchar)
                {
                    case "a":
                        $output .= Date_Calc::getWeekdayAbbrname($day,$month,$year);
                        break;
                    case "A":
                        $output .= Date_Calc::getWeekdayFullname($day,$month,$year);
                        break;
                    case "b":
                        $output .= Date_Calc::getMonthAbbrname($month);
                        break;
                    case "B":
                        $output .= Date_Calc::getMonthFullname($month);
                        break;
                    case "d":
                        $output .= sprintf("%02d",$day);
                        break;
                    case "e":
                        $output .= $day;
                        break;
                    case "E":
                        $output .= Date_Calc::dateToDays($day,$month,$year);
                        break;
                    case "j":
                        $output .= Date_Calc::julianDate($day,$month,$year);
                        break;
                    case "m":
                        $output .= sprintf("%02d",$month);
                        break;
                    case "n":
                        $output .= "\n";
                        break;
                    case "t":
                        $output .= "\t";
                        break;
                    case "w":
                        $output .= Date_Calc::dayOfWeek($day,$month,$year);
                        break;
                    case "U":
                        $output .= Date_Calc::weekOfYear($day,$month,$year);
                        break;
                    case "y":
                        $output .= substr($year,2,2);
                        break;
                    case "Y":
                        $output .= $year;
                        break;
                    case "%":
                        $output .= "%";
                        break;
                    default:
                        $output .= $char.$nextchar;
                }
                $strpos++;
            }
            else
            {
                $output .= $char;
            }
        }
        return $output;

    } // end func dateFormat

    /**
     * Returns the current local year in format CCYY
     *
     * @access public
     *
     * @return string year in format CCYY
     */

    function getYear()
    {
        return Date_Calc::dateNow("%Y");

    } // end func getYear

    /**
     * Returns the current local month in format MM
     *
     * @access public
     *
     * @return string month in format MM
     */

    function getMonth()
    {
        return Date_Calc::dateNow("%m");

    } // end func getMonth

    /**
     * Returns the current local day in format DD
     *
     * @access public
     *
     * @return string day in format DD
     */

    function getDay()
    {
        return Date_Calc::dateNow("%d");

    } // end func getDay

    /**
     * Returns the full month name for the given month
     *
     * @param string month in format MM
     *
     * @access public
     *
     * @return string full month name
     */

    function getMonthFullname($month)
    {
        $month = (int)$month;

        if(empty($month))
            $month = (int) Date_Calc::dateNow("%m");

        $month_names = Date_Calc::getMonthNames();
        return $month_names[$month];
        // getMonthNames returns months with correct indexes
        //return $month_names[($month - 1)];

    } // end func getMonthFullname

    /**
     * Returns the abbreviated month name for the given month
     *
     * @param string month in format MM
     * @param int optional length of abbreviation, default is 3
     *
     * @access public
     *
     * @return string abbreviated month name
     * @see Date_Calc::getMonthFullname
     */

    function getMonthAbbrname($month,$length=3)
    {
        $month = (int)$month;

        if(empty($month))
            $month = Date_Calc::dateNow("%m");
        return substr(Date_Calc::getMonthFullname($month), 0, $length);
    } // end func getMonthAbbrname

    /**
     * Returns the full weekday name for the given date
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     *
     * @access public
     *
     * @return string full month name
     */

    function getWeekdayFullname($day="",$month="",$year="")
    {
        if(empty($year))
            $year = Date_Calc::dateNow("%Y");
        if(empty($month))
            $month = Date_Calc::dateNow("%m");
        if(empty($day))
            $day = Date_Calc::dateNow("%d");

        $weekday_names = Date_Calc::getWeekDays();
        $weekday = Date_Calc::dayOfWeek($day,$month,$year);

        return $weekday_names[$weekday];

    } // end func getWeekdayFullname

    /**
     * Returns the abbreviated weekday name for the given date
     *
     * @param string year in format CCYY, default current local year
     * @param string month in format MM, default current local month
     * @param string day in format DD, default current local day
     * @param int optional length of abbreviation, default is 3
     *
     * @access public
     *
     * @return string full month name
     * @see Date_Calc::getWeekdayFullname
     */

    function getWeekdayAbbrname($day="",$month="",$year="",$length=3)
    {
        if(empty($year))
            $year = Date_Calc::dateNow("%Y");
        if(empty($month))
            $month = Date_Calc::dateNow("%m");
        if(empty($day))
            $day = Date_Calc::dateNow("%d");
        return substr(Date_Calc::getWeekdayFullname($day,$month,$year),0,$length);
    } // end func getWeekdayFullname

    /**
    * Returns the numeric month from the month name or an abreviation
    *
    * Both August and Aug would return 8.
    * Month name is case insensitive.
    *
    * @param    string  month name
    * @return   integer month number
    */
    function getMonthFromFullName($month)
    {
        $month = strtolower($month);
        $months = Date_Calc::getMonthNames();
        while(list($id, $name) = each($months)){
            if(ereg($month, strtolower($name))){
                return($id);
            }
        }
        return(0);
    }

    /**
    * Retunrs an array of month names
    *
    * Used to take advantage of the setlocale function to return
    * language specific month names.
    * XXX cache values to some global array to avoid preformace hits when called more than once.
    *
    * @returns array An array of month names
    */
    function getMonthNames()
    {
        for($i=1;$i<13;$i++){
            $months[$i] = strftime('%B', mktime(0, 0, 0, $i, 1, 2001));
        }
        return($months);
    }

    /**
    * Returns an array of week days
    *
    * Used to take advantage of the setlocale function to
    * return language specific week days
    * XXX cache values to some global array to avoid preformace hits when called more than once.
    *
    * @returns array An array of week day names
    */
    function getWeekDays()
    {
        for($i=0;$i<7;$i++){
            $weekdays[$i] = strftime('%A', mktime(0, 0, 0, 1, $i, 2001));
        }
        return($weekdays);
    }

} // end class Date_calendar

?>