SPGridView problem with Header dropdown context menu

Question

Hello experts,

I've created webpart with SPGridView but I have one problem with it.

When I click on DateTime column Header, items in the header context dropdownmenu (which appears when you click on the header of the column) aren't sorted correctly.

Datasource is assigned via ObjecDataSource. Filtering on other types of columns (string or int32) works properly.

It seems that Menu items in DateTime column header are sorted as string and not datetime values. I also know that SPGridView uses javascript SPGridview.js from /Layout folder...

For further info please check this picture:

http://image.all4all.cz/show.php/39%5FSPGRIDVIEWHeaderDateTimeDropDownproblem.png.html

Please could somebody help me with this problem...

Thank you Vasek S.