dateobject.php

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            // iterate the max last 10 years
            do {
                --$i;
                $day = $timestamp;

                $timestamp += 31536000;
                $leapyear = self::isYearLeapYear($i);
                if ($leapyear === true) {
                    $timestamp += 86400;
                }

                if ($timestamp >= 0) {
                    $year = $i;
                    break;
                }
            } while ($timestamp < 0);

            $secondsPerYear = 86400 * ($leapyear ? 366 : 365) + $day;

            $timestamp = $day;
            // iterate through months
            for ($i = 12; --$i >= 0;) {
                $day = $timestamp;

                $timestamp += self::$_monthTable[$i] * 86400;
                if (($leapyear === true) and ($i == 1)) {
                    $timestamp += 86400;
                }

                if ($timestamp >= 0) {
                    $month  = $i;
                    $numday = self::$_monthTable[$i];
                    if (($leapyear === true) and ($i == 1)) {
                        ++$numday;
                    }
                    break;
                }
            }

            $timestamp  = $day;
            $numberdays = $numday + ceil(($timestamp + 1) / 86400);

            $timestamp += ($numday - $numberdays + 1) * 86400;
            $hours      = floor($timestamp / 3600);
        } else {

            // iterate through years
            for ($i = 1970;;$i++) {
                $day = $timestamp;

                $timestamp -= 31536000;
                $leapyear = self::isYearLeapYear($i);
                if ($leapyear === true) {
                    $timestamp -= 86400;
                }

                if ($timestamp < 0) {
                    $year = $i;
                    break;
                }
            }

            $secondsPerYear = $day;

            $timestamp = $day;
            // iterate through months
            for ($i = 0; $i <= 11; $i++) {
                $day = $timestamp;
                $timestamp -= self::$_monthTable[$i] * 86400;

                if (($leapyear === true) and ($i == 1)) {
                    $timestamp -= 86400;
                }

                if ($timestamp < 0) {
                    $month  = $i;
                    $numday = self::$_monthTable[$i];
                    if (($leapyear === true) and ($i == 1)) {
                        ++$numday;
                    }
                    break;
                }
            }

            $timestamp  = $day;
            $numberdays = ceil(($timestamp + 1) / 86400);
            $timestamp  = $timestamp - ($numberdays - 1) * 86400;
            $hours = floor($timestamp / 3600); 
        }

        $timestamp -= $hours * 3600;

        $month  += 1;
        $minutes = floor($timestamp / 60);
        $seconds = $timestamp - $minutes * 60;

        if ($fast === true) {
            return array(
                'seconds' => $seconds,
                'minutes' => $minutes,
                'hours'   => $hours,
                'mday'    => $numberdays,
                'mon'     => $month,
                'year'    => $year,
                'yday'    => floor($secondsPerYear / 86400),
            );
        }

        $dayofweek = self::dayOfWeek($year, $month, $numberdays);

        return array(
                'seconds' => $seconds,
                'minutes' => $minutes,
                'hours'   => $hours,
                'mday'    => $numberdays,
                'wday'    => $dayofweek,
                'mon'     => $month,
                'year'    => $year,
                'yday'    => floor($secondsPerYear / 86400),
                'weekday' => gmdate('l', 86400 * (3 + $dayofweek)),
                'month'   => gmdate('F', mktime(0, 0, 0, $month, 1, 1971)),
                0         => $otimestamp
        );
    }


    /**
     * Internal getWeekNumber function for handling 64bit timestamps
     *
     * Returns the ISO 8601 week number of a given date
     *
     * @param  integer  $year
     * @param  integer  $month
     * @param  integer  $day
     * @return integer
     */
    protected function weekNumber($year, $month, $day)
    {
        if ((1901 < $year) and ($year < 2038)) {
            return (int) date('W', mktime(0, 0, 0, $month, $day, $year));
        }
        
        $dayofweek = self::dayOfWeek($year, $month, $day);
        $firstday  = self::dayOfWeek($year, 1, 1);
        if (($month == 1) and (($firstday < 1) or ($firstday > 4)) and ($day < 4)) {
            $firstday  = self::dayOfWeek($year - 1, 1, 1);
            $month     = 12;
            $day       = 31;

        } else if (($month == 12) and ((self::dayOfWeek($year + 1, 1, 1) < 5) and 
                   (self::dayOfWeek($year + 1, 1, 1) > 0))) {
            return 1;
        }

        return intval (((self::dayOfWeek($year, 1, 1) < 5) and (self::dayOfWeek($year, 1, 1) > 0)) + 
               4 * ($month - 1) + (2 * ($month - 1) + ($day - 1) + $firstday - $dayofweek + 6) * 36 / 256);
    }


    /**
     * Internal _range function
     * Sets the value $a to be in the range of [0, $b]
     * 
     * @param float $a - value to correct
     * @param float $b - maximum range to set
     */
    private function _range($a, $b) {
        while ($a < 0) {
            $a += $b;
        }
        while ($a >= $b) {
            $a -= $b;
        }
        return $a;
    }


    /**
     * Calculates the sunrise or sunset based on a location
     * 
     * @param  array  $location  Location for calculation MUST include 'latitude', 'longitude', 'horizon'
     * @param  bool   $horizon   true: sunrise; false: sunset
     * @return mixed  - false: midnight sun, integer: 
     */
    protected function calcSun($location, $horizon, $rise = false)
    {
        // timestamp within 32bit
        if (abs($this->_unixTimestamp) <= 0x7FFFFFFF) {
            if ($rise === false) {
                return date_sunset($this->_unixTimestamp, SUNFUNCS_RET_TIMESTAMP, $location['latitude'],
                                   $location['longitude'], 90 + $horizon, $this->_offset / 3600);
            }
            return date_sunrise($this->_unixTimestamp, SUNFUNCS_RET_TIMESTAMP, $location['latitude'],
                                $location['longitude'], 90 + $horizon, $this->_offset / 3600);
        }

        // self calculation - timestamp bigger than 32bit
        // fix circle values
        $quarterCircle      = 0.5 * M_PI;
        $halfCircle         =       M_PI;
        $threeQuarterCircle = 1.5 * M_PI;
        $fullCircle         = 2   * M_PI;

        // radiant conversion for coordinates
        $radLatitude  = $location['latitude']   * $halfCircle / 180;
        $radLongitude = $location['longitude']  * $halfCircle / 180;

        // get solar coordinates
        $tmpRise       = $rise ? $quarterCircle : $threeQuarterCircle;
        $radDay        = $this->date('z',$this->_unixTimestamp) + ($tmpRise - $radLongitude) / $fullCircle;

        // solar anomoly and longitude
        $solAnomoly    = $radDay * 0.017202 - 0.0574039;
        $solLongitude  = $solAnomoly + 0.0334405 * sin($solAnomoly);
        $solLongitude += 4.93289 + 3.49066E-4 * sin(2 * $solAnomoly);

        // get quadrant
        $solLongitude = $this->_range($solLongitude, $fullCircle);

        if (($solLongitude / $quarterCircle) - intval($solLongitude / $quarterCircle) == 0) {
            $solLongitude += 4.84814E-6;
        }

        // solar ascension
        $solAscension = sin($solLongitude) / cos($solLongitude);
        $solAscension = atan2(0.91746 * $solAscension, 1);

        // adjust quadrant
        if ($solLongitude > $threeQuarterCircle) {
            $solAscension += $fullCircle;
        } else if ($solLongitude > $quarterCircle) {
            $solAscension += $halfCircle;
        }

        // solar declination
        $solDeclination  = 0.39782 * sin($solLongitude);
        $solDeclination /=  sqrt(-$solDeclination * $solDeclination + 1);
        $solDeclination  = atan2($solDeclination, 1);

        $solHorizon = $horizon - sin($solDeclination) * sin($radLatitude);
        $solHorizon /= cos($solDeclination) * cos($radLatitude);

        // midnight sun, always night
        if (abs($solHorizon) > 1) {
            return false;
        }

        $solHorizon /= sqrt(-$solHorizon * $solHorizon + 1);
        $solHorizon  = $quarterCircle - atan2($solHorizon, 1);

        if ($rise) {
            $solHorizon = $fullCircle - $solHorizon;
        }

        // time calculation
        $localTime     = $solHorizon + $solAscension - 0.0172028 * $radDay - 1.73364;
        $universalTime = $localTime - $radLongitude;

        // determinate quadrant
        $universalTime = $this->_range($universalTime, $fullCircle);

        // radiant to hours
        $universalTime *= 24 / $fullCircle;

        // convert to time
        $hour = intval($universalTime);
        $universalTime    = ($universalTime - $hour) * 60;
        $min  = intval($universalTime);
        $universalTime    = ($universalTime - $min) * 60;
        $sec  = intval($universalTime);

        return $this->mktime($hour, $min, $sec, $this->date('m', $this->_unixTimestamp),
                             $this->date('j', $this->_unixTimestamp), $this->date('Y', $this->_unixTimestamp),
                             -1, true);
    }


    /**
     * Sets a new timezone for calculation of $this object's gmt offset.
     * For a list of supported timezones look here: http://php.net/timezones
     * If no timezone can be detected or the given timezone is wrong UTC will be set.
     * 
     * @param  string  $zone      OPTIONAL timezone for date calculation; defaults to date_default_timezone_get()
     * @return string  actual set timezone string
     * @throws Zend_Date_Exception
     */
    public function setTimezone($zone = null)
    {
        $oldzone = @date_default_timezone_get();
        if ($zone === null) {
            $zone = $oldzone;
        }

        // throw an error on false input, but only if the new date extension is avaiable
        if (function_exists('timezone_open')) {
            if (!@timezone_open($zone)) {
                throw new Zend_Date_Exception("timezone ($zone) is not a known timezone", $zone);
            }
        }
        // this can generate an error if the date extension is not avaiable and a false timezone is given
        $result = date_default_timezone_set($zone);
        if ($result === true) {
            $this->_offset   = mktime(0, 0, 0, 1, 2, 1970) - gmmktime(0, 0, 0, 1, 2, 1970);
            $this->_timezone = $zone;
        }
        date_default_timezone_set($oldzone);

        return $result;
    }


    /**
     * Return the timezone of $this object.
     * The timezone is initially set when the object is instantiated.
     * 
     * @return  string  actual set timezone string
     */
    public function getTimezone()
    {
        return $this->_timezone;
    }


    /**
     * Return the offset to GMT of $this object's timezone.
     * The offset to GMT is initially set when the object is instantiated using the currently,
     * in effect, default timezone for PHP functions.
     * 
     * @return  integer  seconds difference between GMT timezone and timezone when object was instantiated
     */
    public function getGmtOffset()
    {
        return $this->_offset;
    }
}