* @param  mixed $format Format string to set it from a string or the
     *                       second date set it from a date diff.
     *
     * @see    set()
     * @access public
     */
    function Date_Span($time = 0, $format = null)
    {
        $this->set($time, $format);
    }

    // }}}
    // {{{ set()

    /**
     * Set the time span to a new value in a 'smart' way.
     *
     * Sets the time span depending on the argument types, calling
     * to the appropriate setFromXxx() method.
     *
     * @param  mixed $time   Time span expression.
     * @param  mixed $format Format string to set it from a string or the
     *                       second date set it from a date diff.
     *
     * @return bool  true on success.
     *
     * @see    setFromObject()
     * @see    setFromArray()
     * @see    setFromString()
     * @see    setFromSeconds()
     * @see    setFromDateDiff()
     * @access public
     */
    function set($time = 0, $format = null)
    {
        if (is_a($time, 'date_span')) {
            return $this->copy($time);
        } elseif (is_a($time, 'date') and is_a($format, 'date')) {
            return $this->setFromDateDiff($time, $format);
        } elseif (is_array($time)) {
            return $this->setFromArray($time);
        } elseif (is_string($time)) {
            return $this->setFromString($time, $format);
        } elseif (is_int($time)) {
            return $this->setFromSeconds($time);
        } else {
            return $this->setFromSeconds(0);
        }
    }

    // }}}
    // {{{ setFromArray()

    /**
     * Set the time span from an array.
     *
     * Set the time span from an array. Any value can be a float (but it
     * has no sense in seconds), for example array(23.5, 20, 0) is
     * interpreted as 23 hours, .5*60 + 20 = 50 minutes and 0 seconds.
     *
     * @param  array $time Items are counted from right to left. First
     *                     item is for seconds, second for minutes, third
     *                     for hours and fourth for days. If there are
     *                     less items than 4, zero (0) is assumed for the
     *                     absent values.
     *
     * @return bool  True on success.
     *
     * @access public
     */
    function setFromArray($time)
    {
        if (!is_array($time)) {
            return false;
        }
        $tmp1 = new Date_Span;
        if (!$tmp1->setFromSeconds(@array_pop($time))) {
            return false;
        }
        $tmp2 = new Date_Span;
        if (!$tmp2->setFromMinutes(@array_pop($time))) {
            return false;
        }
        $tmp1->add($tmp2);
        if (!$tmp2->setFromHours(@array_pop($time))) {
            return false;
        }
        $tmp1->add($tmp2);
        if (!$tmp2->setFromDays(@array_pop($time))) {
            return false;
        }
        $tmp1->add($tmp2);
        return $this->copy($tmp1);
    }

    // }}}
    // {{{ setFromString()

    /**
     * Set the time span from a string based on an input format.
     *
     * Set the time span from a string based on an input format. This is
     * some like a mix of format() method and sscanf() PHP function. The
     * error checking and validation of this function is very primitive,
     * so you should be carefull when using it with unknown $time strings.
     * With this method you are assigning day, hour, minute and second
     * values, and the last values are used. This means that if you use
     * something like setFromString('10, 20', '%H, %h') your time span
     * would be 20 hours long. Allways remember that this method set
     * <b>all</b> the values, so if you had a $time span 30 minutes long
     * and you make $time->setFromString('20 hours', '%H hours'), $time
     * span would be 20 hours long (and not 20 hours and 30 minutes).
     * Input format options:<br>
     *  <code>%C</code> Days with time, same as "%D, %H:%M:%S".<br>
     *  <code>%d</code> Total days as a float number
     *                  (2 days, 12 hours = 2.5 days).<br>
     *  <code>%D</code> Days as a decimal number.<br>
     *  <code>%e</code> Total hours as a float number
     *                  (1 day, 2 hours, 30 minutes = 26.5 hours).<br>
     *  <code>%f</code> Total minutes as a float number
     *                  (2 minutes, 30 seconds = 2.5 minutes).<br>
     *  <code>%g</code> Total seconds as a decimal number
     *                  (2 minutes, 30 seconds = 90 seconds).<br>
     *  <code>%h</code> Hours as decimal number.<br>
     *  <code>%H</code> Hours as decimal number limited to 2 digits.<br>
     *  <code>%m</code> Minutes as a decimal number.<br>
     *  <code>%M</code> Minutes as a decimal number limited to 2 digits.<br>
     *  <code>%n</code> Newline character (\n).<br>
     *  <code>%p</code> Either 'am' or 'pm' depending on the time. If 'pm'
     *                  is detected it adds 12 hours to the resulting time
     *                  span (without any checks). This is case
     *                  insensitive.<br>
     *  <code>%r</code> Time in am/pm notation, same as "%H:%M:%S %p".<br>
     *  <code>%R</code> Time in 24-hour notation, same as "%H:%M".<br>
     *  <code>%s</code> Seconds as a decimal number.<br>
     *  <code>%S</code> Seconds as a decimal number limited to 2 digits.<br>
     *  <code>%t</code> Tab character (\t).<br>
     *  <code>%T</code> Current time equivalent, same as "%H:%M:%S".<br>
     *  <code>%%</code> Literal '%'.<br>
     *
     * @param  string $time   String from where to get the time span
     *                        information.
     * @param  string $format Format string.
     *
     * @return bool   True on success.
     *
     * @access public
     */
    function setFromString($time, $format = null)
    {
        if (is_null($format)) {
            $format = $GLOBALS['_DATE_SPAN_INPUT_FORMAT'];
        }
        // If format is a string, it parses the string format.
        if (is_string($format)) {
            $str = '';
            $vars = array();
            $pm = 'am';
            $day = $hour = $minute = $second = 0;
            for ($i = 0; $i < strlen($format); $i++) {
                $char = $format{$i};
                if ($char == '%') {
                    $nextchar = $format{++$i};
                    switch ($nextchar) {
                        case 'c':
                            $str .= '%d, %d:%d:%d';
                            array_push(
                                $vars, 'day', 'hour', 'minute', 'second');
                            break;
                        case 'C':
                            $str .= '%d, %2d:%2d:%2d';
                            array_push(
                                $vars, 'day', 'hour', 'minute', 'second');
                            break;
                        case 'd':
                            $str .= '%f';
                            array_push($vars, 'day');
                            break;
                        case 'D':
                            $str .= '%d';
                            array_push($vars, 'day');
                            break;
                        case 'e':
                            $str .= '%f';
                            array_push($vars, 'hour');
                            break;
                        case 'f':
                            $str .= '%f';
                            array_push($vars, 'minute');
                            break;
                        case 'g':
                            $str .= '%f';
                            array_push($vars, 'second');
                            break;
                        case 'h':
                            $str .= '%d';
                            array_push($vars, 'hour');
                            break;
                        case 'H':
                            $str .= '%2d';
                            array_push($vars, 'hour');
                            break;
                        case 'm':
                            $str .= '%d';
                            array_push($vars, 'minute');
                            break;
                        case 'M':
                            $str .= '%2d';
                            array_push($vars, 'minute');
                            break;
                        case 'n':
                            $str .= "\n";
                            break;
                        case 'p':
                            $str .= '%2s';
                            array_push($vars, 'pm');
                            break;
                        case 'r':
                            $str .= '%2d:%2d:%2d %2s';
                            array_push(
                                $vars, 'hour', 'minute', 'second', 'pm');
                            break;
                        case 'R':
                            $str .= '%2d:%2d';
                            array_push($vars, 'hour', 'minute');
                            break;
                        case 's':
                            $str .= '%d';
                            array_push($vars, 'second');
                            break;
                        case 'S':
                            $str .= '%2d';
                            array_push($vars, 'second');
                            break;
                        case 't':
                            $str .= "\t";
                            break;
                        case 'T':
                            $str .= '%2d:%2d:%2d';
                            array_push($vars, 'hour', 'minute', 'second');
                            break;
                        case '%':
                            $str .= "%";
                            break;
                        default:
                            $str .= $char . $nextchar;
                    }
                } else {
                    $str .= $char;
                }
            }
            $vals = sscanf($time, $str);
            foreach ($vals as $i => $val) {
                if (is_null($val)) {
                    return false;
                }
                $$vars[$i] = $val;
            }
            if (strcasecmp($pm, 'pm') == 0) {
                $hour += 12;
            } elseif (strcasecmp($pm, 'am') != 0) {
                return false;
            }
            $this->setFromArray(array($day, $hour, $minute, $second));
        // If format is a integer, it uses a pred