Working with the Core grid I noticed that the excel export autowidth is not working for date columns. Every other column is working but not dates. Here is my function for the export...
function gridReport_ExcelExport(e) {    var sheet = e.workbook.sheets[0];    for (var rowIndex = 0; rowIndex < sheet.rows.length; rowIndex++) {        var row = sheet.rows[rowIndex];        var expandRow = false;        for (var cellIndex = 0; cellIndex < row.cells.length; cellIndex++) {            var cell = row.cells[cellIndex];            if (rowIndex > 0)                cell.vAlign = "top";            if (cell.value && cell.value.toString().indexOf("<br />") >= 0) {                cell.value = cell.value.replace("<br />", "\n");                cell.wrap = true;                    expandRow = true;            }        }        if (rowIndex > 0)            sheet.rows[rowIndex].height = 50;    }        for (var colIndex = 0; colIndex < sheet.columns.length; colIndex++) {        var column = sheet.columns[colIndex];        delete column.width;        column.autoWidth = true;    }}
I found a kendo dojo and was able to duplicate the issue there also. (http://dojo.telerik.com/oGafisuF) I modified it as this...
<body>  <div id="grid"></div>  <script>    var dt = new Date();  $("#grid").kendoGrid({    dataSource: [      { foo: "foo", bar: "bar", somedate: dt }    ],    toolbar:["excel"],    columns: [      { field: "foo", width: "100px"},      { field: "bar", width: "200px"},      { field: "somedate", width: "100px", template: "#= kendo.toString(kendo.parseDate(somedate, 'yyyy-MM-dd'), 'MM/dd/yyyy') #"}    ],    excelExport: function(e) {      var sheet = e.workbook.sheets[0];      for (var i = 0; i < sheet.columns.length; i++) {        delete sheet.columns[i].width;        sheet.columns[i].autoWidth = true;      }    }  });  </script></body>