using System.Collections.Generic;

using System.Linq;

using System;

public class Program

{

    public static void Main()

    {

        foreach( var t in Split(new DateTime(2018,8,1), new DateTime(2018,8,17),6)){

            Console.WriteLine(t.Item1.ToString() + " " + t.Item2.ToString());

        }

    }   

    public static IEnumerable<Tuple<DateTime, DateTime>> Split(DateTime start, DateTime end, int chunk)

    {

        DateTime chunkEnd;

        while ((chunkEnd = start.AddDays(chunk)) < end)

        {

            yield return Tuple.Create(start, chunkEnd);

            start = chunkEnd.AddDays(1);

        }

        yield return Tuple.Create(start, start.AddDays(chunk));

    }

}