formát data php dd / mm / RRRR
date("d/m/Y", strtotime($str));
php převést datum z dd / mm / RRRR na RRRR-mm-dd
$date = DateTime::createFromFormat('d/m/Y', "24/04/2012");
echo $date->format('Y-m-d');
yyyymmdd na YYYY-mm-DD php
<?php
// both lines output 813470400
echo strtotime("19951012"), "\n",
strtotime("12 October 1995");
// prints 1995 Oct 12
echo date("Y-m-d", strtotime("19951012"));
?>