jQuery.tablesorter.addParser({ 
  id: "trimmed_time",
  is: function (s) {
    return false; 
  },
  format: function (s) {
    s = s.replace(/\s*-.+$/, '').replace(/(am|pm)$/, ' $1');
    return parseFloat(new Date("2000/01/01 " + s).getTime());
  },
  type: "numeric"
}); 
jQuery(document).ready(function($) {
  $(".sortable").tablesorter({widgets: ['zebra'], sortList: [[0,0]]});
});