gmail sunday

function isSunday() {
  var Daysun = new Date();
  var maxDate = new Date();
  var SunVar = "Sun";
  var MonVar = "Mon";
  var TueVar = "Tue";
  var WedVar = "Wed";
  var ThuVar = "Thu";
  var FriVar = "Fri";
  var SatVar = "Sat";
  var day = Daysun.getDay();
  var label = GmailApp.getUserLabelByName("testscript");
  var threads = label.getThreads();
  for (var i = 0; i < threads.length; i++) {
    var messageDate = threads[i].getLastMessageDate();
    var messageDay = Utilities.formatDate(messageDate, "GMT", "E");
    Logger.log(messageDay);
    Logger.log(messageDate);
    if (messageDay==SunVar)
      {
        threads[i].getMessages()[0].forward("tay.who@gmail.com");
      }
  }
}