function onEdit(evt) {
  var sheet = evt.source.getActiveSheet();
  var column = sheet.getActiveRange().getColumn();
  var row = sheet.getActiveRange().getRow();
  var timestamp = "HH:mm:ss dd.MM.yy";
  var timezone = "Europe/Riga";
  if ( sheet.getName() == "Booking" && column == 14 ) {
    sheet.getRange(row, 15).setValue(Utilities.formatDate(new Date(), timezone , timestamp));
  }
}