DifferenceBetweenTZ1AndTZ3.php

<?php

// switch this variable to see the difference
$useTimeZone3 =  true;

date_default_timezone_set('Europe/Berlin');

if ($useTimeZone3) {
    $date = new \DateTime('2016-09-09 00:00:00');
} else {
    $date = new \DateTime(date('c', 1473372000));
}

for ($i = 0; $i < 52; $i++) {
    $date->modify('+1 week');
    echo $date->format('l - d.m.Y - H:i:s');
    $ts = $date->format('U');
    echo '-' . $ts . '-';
    // $ts wird in DB gespeichert
    // Anzeige im Frontend holt $ts wieder aus DB
    $dateTimeFromDb = new \DateTime(date('c', $ts));
    echo $dateTimeFromDb->format('l - d.m.Y - H:i:s');
    echo '<br />';
}

echo '<hr />';

$xths = array(
    'first' => 1,
    'second' => 0,
    'third' => 0,
    'fourth' => 1,
    'fifth' => 0
);

$weekDays = array(
    'monday' => 0,
    'tuesday' => 0,
    'wednesday' => 0,
    'thursday' => 0,
    'friday' => 1,
    'saturday' => 0,
    'sunday' => 0
);

$months = array(
    1 => 'july',
    2 => 'august',
    3 => 'september',
    4 => 'october',
    5 => 'november',
    6 => 'december',
);

if ($useTimeZone3) {
    $date = new \DateTime('2016-09-09 00:00:00');
} else {
    $date = new \DateTime(date('c', 1473372000));
}

foreach ($months as $month) {
    foreach ($xths as $xthIndex => $xth) {
        foreach ($weekDays as $weekdayIndex => $weekday) {
            if ($xth && $weekday) {
                // example: 'second wednesday of March 2013'
                $modifyString = $xthIndex . ' ' . $weekdayIndex . ' of ' . $month . ' 2016';
                $date->modify($modifyString);
                
                echo $date->format('l - d.m.Y - H:i:s');
                $ts = $date->format('U');
                // $ts wird in DB gespeichert
                // Anzeige im Frontend holt $ts wieder aus DB
                $dateTimeFromDb = new \DateTime(date('c', $ts));
                echo $dateTimeFromDb->format('l - d.m.Y - H:i:s');
                echo '<br />';
            }
        }
    }
}