3v4l.org

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<?php $i = 15; $dt = new DateTime(); $interval = new DateInterval('P'.abs($i).'W'); ($i < 0) ? $dt->sub($interval) : $dt->add($interval); echo $dt->format('d-m-Y');
Output for 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6
23-12-2015

preferences:
245.34 ms | 404 KiB | 376 Q