Online PHP editor | refs for pk51P

<?php $dateStamp = "2015-06-01 00:00:00"; $datesArr = []; for ($i=1; $i<21 ; $i++) { $numMonths = $i*3; $date = new DateTime($dateStamp); $date->modify('+' . $numMonths .' month'); // or you can use '-90 day' for deduct $datesArr[] = $date->format('Y-m-d h:i:s'); } echo '<pre>'; print_r($datesArr); echo '</pre>';