You do not need to convert the DateTime to String, but instead you should create a new DateTime object which contains only the Date portion of the original date.
Also another approach to handle this is described in this forum post
- which uses a custom model binder to change the filter descriptors.
Although, it may seems a bit odd the way date filtering is handled, this is due to the fact that there is not way to automatically know if it should match the exact date and time or strip the time portion. Thus, it keeps the time as this is the less destructive of the both and give the developer the option to decide the behavior by providing the correct data.