#C#, 125 Bytes

    using System;class P{static void Main(){for(;;)Console.Write("\r{0:d\\:h\\:mm\\:ss}",new DateTime(2019,3,31)-DateTime.Now);}}

Ungolfed code:

    using System;
    class P
    {
        static void Main()
        {
            for(;;)
                Console.Write("\r{0:d\\:h\\:mm\\:ss}",new DateTime(2019,3,31)-DateTime.Now); 
        }
    }



  [1]: http://codegolf.stackexchange.com/a/115049/58322