日期之间的数据条和日期时间格式不可排序

I have an Invoices table of Due dates and Paid dates. I have a 3rd column that is the time between paid and due date. I use DateTime and format to get how many days late the payment was.

            $pDate = date("Y-m-d H:i:s",$paidDate);
            $dDate = date("Y-m-d H:i:s",$dueDate);
            $pDate = new DateTime($pDate);
            $dDate = new DateTime($dDate);
            $diff = $pDate->diff($dDate);
            $pastDueFormat = $diff->format('%a');

I have tried change format to

$pastDueFormat = $diff->format('%d');

I have all this data in a table formatted by DataTables

$('#invoices').dataTable();

The problem is, I cant get sort to recognized 39 days as a number, or even 39 for that matter. my sort results are always

94 91 9 88 85 8....

when clearly i want 94,91,88,85,9,8.....

Looks like DataTables isn't so smart after all. You can explicitly provide the column type like this:

$('#invoices').dataTable({'columnDefs': [{'type': 'num', 'targets': 0}]});

The value of the 'targets' key should equal the index of your column, 0-based.