cellTooltip not working correctly when cellFilter has just date format

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If I give dateformat string and set cellTooltip: true, the tooltip is not displaying correctly. For example: { field: 'mixedDate', displayName: "Cust Date", cellFilter: 'date:"dd-MM-yyyy HH:mm:ss"', filterCellFiltered:true, cellTooltip: true, width: '30%'}

As showing in the given plunker http://plnkr.co/edit/Olv74Y83jUaXQBvv8Mpg?p=preview