using System;

​

public static class DateTimeExtension

    {

        public static DateTime GetLastWeekReset(this DateTime dateTime)

        {

            if (dateTime.DayOfWeek == DayOfWeek.Tuesday)

            {

                if (dateTime.Hour < 17)

                {

                    dateTime = dateTime.AddDays(-7);

                }

            }

            else if (dateTime.DayOfWeek < DayOfWeek.Tuesday)

            {

                dateTime = dateTime.AddDays(-(7 - (int) dateTime.DayOfWeek));

            }

            else

            {

                dateTime = dateTime.AddDays(-((int) (dateTime.DayOfWeek - DayOfWeek.Tuesday)));

            }

​

            return dateTime;

        }

    }

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine(DateTime.UtcNow.AddDays(8).GetLastWeekReset()); 

    }

}