one month previous day in magento

Question

I want new date from current date, difference of 30 days.

$dt = date("Y/m/j",strtotime("-1 month"));
and 
$firstDayOfPrevMonth = date("01.m.Y", Mage::getModel('core/date')->timestamp(strtotime('first day of previos month')));

above is not working for me.

Answer 1

Try:

<?php
    echo date("Y-m-d h:i:s",strtotime('-30 days'));
?>

This should work...

Answer 2

<?php
    $date = new DateTime();
    $date->modify('-1 months');
    $date->setTimezone(new DateTimezone('Europe/Paris'));
    echo $date->format('Y/m/j'); // 2017/08/7 instead of 2017/09/7 
?>