Using LINQ.Distinct () with DateTime - fetching only the first instance of a date

I am using EF and LINQ in my MVC 3 web application.

I have a request like this

var dates = timetableEvents.GroupBy(x => x.DateTimeStart).Distinct();

      

        
        
        
      

    

x.DateTimeStart

- date in this format:

23/01/2013 12:47:13
23/01/2013 14:00:10
23/01/2013 16:15:00
24/01/2013 02:05:00
24/01/2013 04:55:05
25/01/2013 06:00:00

      

        
        
        
      

    

I need a filter that only selects the first instance of a date.

How to do it?

23/01/2013
24/01/2013
25/01/2013