Description:
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I've encountered an inconsistency on the processing of the week numbers on the setISODate method for the DateTime object
Because of the week and day of the week number arrangement you can get a borderline case to get inconsistent. I've tested it on my 5.6.10 version of php and on an online 7.0.0beta2 version on the next link
http://viper-7.com/G77zZ0
If you change the initial date stored on the $now variable to a day that's not the end of the week it works fine, but otherwise it will return a day prior to the current $now time.

Test script:
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        $regex = '/^(\d)\s+(\d\d):(\d\d)(:\d\d)?$/';            // 0 12:00
        $data = "1 12:00";
        if(preg_match($regex, $data, $matches)) {
            $now = new \DateTime("2015-07-12 02:00:00");
            var_dump($now->format('c'));
            $weekDay = intval($now->format("w"));
            $weekNumber = intval($now->format("W"));
            $year = intval($now->format("Y"));
            if($matches[1] > $weekDay){
                $now->setISODate($year, $weekNumber, $matches[1]);
                $now->setTime($matches[2], $matches[3]);
            }
            else if($matches[1] <= $weekDay){
                $now->setISODate($year, $weekNumber+1, $matches[1]);
                $now->setTime($matches[2], $matches[3]);
            }
            var_dump($now->format('c'));
        }

Expected result:
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It should return 2015-07-13T12:00:00+00:00