Description:
------------
Found in PHP 5.6.31, still exists in version 7 as per testing with https://3v4l.org/35D4t

If you subtract a DateInterval that ends during the spring daylight savings time transition, the wrong DateTime and DateTime->getTimestamp() are returned. See example. If the DateInterval spans the full transition, then it is ok.




Test script:
---------------
$a = new \DateTime('2016-03-13 3:00:00', new DateTimeZone('America/Los_Angeles'));
echo "Original Timestamp: ".$a->getTimeStamp()."\n";
$b = clone $a;
$b->sub(new \DateInterval('PT1S'));
echo "Subtract 1 second Timestamp: ".$b->getTimeStamp()."\n";
print_r([$a,$b]);


Expected result:
----------------
Original Timestamp: 1457863200
Subtract 1 second Timestamp: 1457863199
Array
(
    [0] => DateTime Object
        (
            [date] => 2016-03-13 03:00:00.000000
            [timezone_type] => 3
            [timezone] => America/Los_Angeles
        )

    [1] => DateTime Object
        (
            [date] => 2016-03-13 01:59:59.000000
            [timezone_type] => 3
            [timezone] => America/Los_Angeles
        )

)

Actual result:
--------------
Original Timestamp: 1457863200
Subtract 1 second Timestamp: 1457866799
Array
(
    [0] => DateTime Object
        (
            [date] => 2016-03-13 03:00:00.000000
            [timezone_type] => 3
            [timezone] => America/Los_Angeles
        )

    [1] => DateTime Object
        (
            [date] => 2016-03-13 03:59:59.000000
            [timezone_type] => 3
            [timezone] => America/Los_Angeles
        )

)