function onEdit(e){
    var s = e.source.getActiveSheet(),
        watchCols=[1, 6],
        offsetCol=[3, 3],
        ind=watchCols.indexOf(e.range.columnStart)
        if(s.getName() !=="Maintenance" || ind === -1) return;
    e.range.offset(0, offsetCol[ind])
   .setValue(!e.value ? null : Utilities.formatDate(new Date(), "GMT-8", "MM/dd/yyyy HH:mm:ss"))
     }