I have a customproperty that works and makes it possible for me to have a property that saves only date, but it is of string type and it would be much better if there were a built in function for this.

Meaning it would be possible to do like this:

[Display(
     Name = "Last day of application",
     Description = "The last day for sending in the application",
     GroupName = SystemTabNames.Content,
     Order = 5)]
[UIHint(UIHint.DateOnly)]
public virtual DateTime LastApplicationDay { get; set; }