Google Sheet Script for automatically entering date/time stamp when the adjacent column

I've found a script on here for entering a timestamp in a column based on edits to the adjacent column:Date and time stamp automatically added in column

  if(e.source.getActiveSheet().getName() == "Sheet1" ) {    var col = e.source.getActiveCell().getColumn();    if(col == 1 || col == 4) {      var nCell = e.range.offset(0,1);         if(nCell.getValue() == "" && e.value != "") {        var time = Utilities.formatDate(new Date(), "GMT+1", "HH:mm:ss");        nCell.setValue(time);      } else if(nCell.getValue() != "" && e.value == "") {         nCell.setValue("");      }    }  }    }

I can only get it to enter the time or the date not both. What am I missing? I need to have a timestamp auto entered after we enter completed in the previous cell before the document is transferred to our historical tab.