Could you please point me where is the difference to correct this? Thank you.
Also when you use the date sorting it is a good idea to use the datefmt option to thell the grid what is the format for the date to sort it in right way. The dafault option of datefmt is Y-m-d. Is this your format? If not you will have bad sorting.
Also this is described in the docs: Basic Grid -> Properties->colModel Properties