Excel output date format

[mm-ing]

After grid export to excel a grid column formatted as date looks like a date now, but actually it's a string without the possibility to use the excel filter features for datetime.

Annotation example:
[GridColumn(Position = 10, Title = "Value Date", Format = "{0:dd/MM/yyyy}")]

We changed the ExcelWriter.cs a little bit and got the expected output.
Please substitute the ExcelWriter with the modified one and the problem will be solved.

ExcelWriter.zip