In PHP, you can convert date to any format by using a combination of date and strtotime function.
Please try below format to convert date:
date(format, strtotime(originaldate))
Suppose, you have original date as mm/dd/yy
(say 21/03/10) and you want to convert it to yy/mm/dd H:i:s format (say 10/03/21 00:00:00), then try below code:
$originalDate = "21/03/10";
$newDate = date("d-m-Y H:i:s", strtotime($originalDate));