Hi Eyup,
The first project (KendoGridBasicApp) you posted did not work for me and I didn't want to waste time trying to get it to work.
The second project (KendoGridEditDropDownWidth) did run however straight away I have the same problem with the dates. The first row (productname96) has the customdate displayed as Sat Aug 13 2016 10:22:58 GMT+1200 (New Zealand Standard Time) if I change the date from 13 to the 14 I get an invalid modelstate in the post event with the ErrorMessage = "The value '8/14/2016 10:22:58 AM' is not valid for CustomDate."
If I enter 14/01/2001 I get a client side validation error(CustomDate is not a Date).
If I enter 01/14/2001 I get a modelstate ErrorMessage = "The value '1/14/2001 12:00:00 AM' is not valid for CustomDate."
If I enter 01/01/2001 I get a valid modelstate and the post completes successfully.
Regards,
Sam