convert DIFF_TIME_STR parameter to a readable / usable value

We are using the DTE block to trigger an event, but we would also like to show the remaining time on an Operate graphic in a more traditional DD/MM/YYYY HH:MM:SS format instead of the ISO style and we would also like to have the value in the control module converted to a numerical value so that it can be used with a RET block.  Is there a way to convert the DIFF_TIME_STR to our desired time format as well as read the value in seconds?

Thanks