using System;

public class Program

{

    public static void Main()

    {

        DateTime lastWeek = DateTime.Now.AddDays(-7);

            var dayOfWeek = DateTime.Today.DayOfWeek;

            DateTime startDate = lastWeek.AddDays(-(double)dayOfWeek);

            DateTime endDate = startDate.AddDays(6);

            Console.WriteLine( ChangeTime(startDate, 00, 00, 00, 0));

            Console.WriteLine( ChangeTime(endDate, 23, 59, 59, 999));

    }

    public static DateTime ChangeTime(DateTime dateTime, int hours, int minutes, int seconds, int milliseconds)

    {

        return new DateTime(

            dateTime.Year,

            dateTime.Month,

            dateTime.Day,

            hours,

            minutes,

            seconds,

            milliseconds,

            dateTime.Kind);

    }

}