using System;

public class Program

{

    public static void Main()

    {

        var adjustedDay = GetAdjustedDay(2020, 10);

        Console.WriteLine(adjustedDay);

    }

     public static int GetAdjustedDay(int year, int month) {

         var currentDate = new DateTime(2020, 11, 1); ///DateTime.Now;

         if (currentDate.Month != month && currentDate.Year == year) {

             return DateTime.DaysInMonth(year, month);

         }

         int daysOffset = 0;

         switch (currentDate.DayOfWeek) {

             case DayOfWeek.Friday:

                 if (currentDate.Hour < 18) {

                     daysOffset = -1;

                 } else {

                     daysOffset = 2;

                 }

                 break;

             case DayOfWeek.Saturday:

                 daysOffset = 1;

                 break;

             case DayOfWeek.Sunday:

                 daysOffset = 0;

                 break;

             case DayOfWeek.Monday:

                 if (currentDate.Hour < 18) {

                     daysOffset = -1;

                 } else {

                     daysOffset = 0;

                 }

                 break;

             default:

                 if (currentDate.Hour < 18) {

                     daysOffset = -1;

                 }

                 break;

         }

         if ((currentDate.Day + daysOffset) >= 0) {

             //offset will result in a valid date

             var offsetDate = currentDate.AddDays(daysOffset);

             return offsetDate.Day;

         } else {

             //offset will result in an invalid date

             //use current date's day

             return currentDate.Day;

         }

     }

}