using System;

public class Program

{

    public static void Main()

    {

        DateTimeOffset firstDate = DateTime.Parse("2018-12-31");

        DateTimeOffset secondDate = DateTime.Parse("2019-12-31");

        double difference;

​

        difference = (firstDate - secondDate).TotalDays + 1;

        Console.WriteLine(firstDate + " - " + secondDate + " - " + difference + " days, ");

        Console.WriteLine((int)Math.Ceiling(difference / 7));

    }

}