PHP / Magento - 转换日期格式

This is on a magento RMA email template, Im trying to convert the date format from US to UK. I’ve tried the below but nothing renders out on the frontend - does anyone know where I am going wrong please?

<?php 
    $originalDate = "{{var rma.getDateForCollection()}}";
    $newDate = date("d-m-Y", strtotime($originalDate));
    echo $newDate;
?>