Plugin for jQuery Datatables sorting of US-style date and time. Requires month, day and year. Time is optional and can be in 12 or 24 hour formats. Properly parses mm/m, dd/d and yyyy/yy.

datatables.datetime-flex.js

/**
 * DataTables plug-in to handle U.S.-style dates. Requires month day year.  
 * Time is optional and can be in 12 or 24 hour formats. 
 * Properly parses mm/m, dd/d and yyyy/yy.
 * 
 * Based on original datetime-us plugin by Kevin Gravier.
 *
 *  @name Flexible US Datetime
 *  @summary Sort dates and times in US mm/dd/yyyy with optional time.
 *  @author Mark Stewart
 *
 *  @example
 *    $('#example').dataTable( {
 *       columnDefs: [
 *         { type: 'datetime-us-flex', targets: 0 }
 *       ]
 *    } );
 */

jQuery.extend( jQuery.fn.dataTableExt.oSort, {
  "datetime-us-flex-pre": function ( a ) {
    // If there's no slash, then it's not an actual date, so return zero for sorting
    if(a.indexOf('/') === -1) {
        return '0';
    } else {
      // Set optional items to zero
      var hour = 0,
          min = 0,
          ap = 0;
      // Execute match. Requires month, day, year. Can be mm/dd or m/d. Can be yy or yyyy
      // Time is optional. am/pm is optional
      // TODO - remove extra time column from array
      var b = a.match(/(\d{1,2})\/(\d{1,2})\/(\d{2,4})( (\d{1,2}):(\d{1,2}))? ?(am|pm|AM|PM|Am|Pm)?/),
          month = b[1],
          day = b[2],
          year = b[3];
      // If time exists then output hours and minutes
      if (b[4] != undefined) {
        hour = b[5];
        min = b[6];
      }
      // if using am/pm then change the hour to 24 hour format for sorting
      if (b[7] != undefined) {
        ap = b[7];
        if(hour == '12') hour = '0';
        if(ap == 'pm') hour = parseInt(hour, 10)+12;
      }

      // for 2 digit years, changes to 20__ if less than 70
      if(year.length == 2){
        if(parseInt(year, 10) < 70) year = '20'+year;
        else year = '19'+year;
      }
      // Converts single digits
      if(month.length == 1) month = '0'+month;
      if(day.length == 1) day = '0'+day;
      if(hour.length == 1) hour = '0'+hour;
      if(min.length == 1) min = '0'+min;
      var tt = year+month+day+hour+min;
      
      return tt;
    }      
  },
  "datetime-us-flex-asc": function ( a, b ) {
    return a - b;
  },
  "datetime-us-flex-desc": function ( a, b ) {
    return b - a;
  }
});

mark47 I could kiss you right now. This worked like a dream!!! I will be posting this link everywhere I can.