Date Time Sorting Questions

I have a dataTable with a date column in dd/mm/yyyy format and a time column in hh:mm format with times before 10:00 displaying as 9:59 not 09:59.

I need dataTables to understand those formats point 1.
I need to sort the table by default with the date column and then the time column both descending so the most recent date and time is first point 2.

I have read thru the other discussions on using moment.js and datetime-moment.js.

Am I going about this the right way by using these plugins?

just before the data table instantiation I declare:

$.fn.dataTable.moment( 'DD/MM/YYYY' );
$.fn.dataTable.moment( 'HH:mm' );

and in the table instantiation I have:

"order": [ [ 3, "desc" ], [ 4, "desc" ] ],

However I am getting in the time column:

9:58
9:57
9:56
10:04
10:03
10:02

What am i Missing here?

Thanks

Ken