using System;

​

namespace ConsoleAppWeekday

{

    public class Program

    {

        public static void Main(string[] args)

        {

            try

            {

                if (args == null || args.Length <= 1 || args[0].ToLower() == "--help")

                {

                    ShowHelp();

                }

                else

                {

                    Console.WriteLine(args[0]);

                    Console.WriteLine(args[1]);

                    int year = int.Parse(args[0]);

                    int day = int.Parse(args[1]);

​

                    int numberOfDays = Weekday.WeekdaysInFirstOfTheMonth(year, day);

                    string weekday = Weekday.GetWeekday(day);

​

                    Console.WriteLine("In the year {0}, {1} fell on the first of the month {2} times.", year, day, numberOfDays);

                }

            }

            catch(FormatException ex)

            {

                Console.WriteLine("Wrong type of arguments...");

                ShowHelp();

            }

            catch(Exception ex)

            {

                Console.WriteLine("Unexpected error...");

                ShowHelp();

            }

        }

​

        private static void ShowHelp()

        {

            Console.WriteLine("USAGE: program YYYY Weekday");

        }

    }

​

    public static class Weekday

    {

        // Find the weekday of the given date - Schwerdtfeger's Algorithm

        public static int GetWeekday(int d, int m, int y)

        {

            int[] t = { 0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4 };

            y -= (m < 3) ? 1 : 0;

​

            return (y + y / 4 - y / 100 + y / 400 + t[m - 1] + d) % 7;

        }

​

        // Convert an int into a weekday

        public static string GetWeekday(int weekday)

        {

            return Enum.GetName(typeof(DayOfWeek), weekday);

        }

​

        // Find the number of times weekday fell on the first of the month in the given year

        public static int WeekdaysInFirstOfTheMonth(int year, int day)

        {

            int counter = 0;

​

            for (int i = 1; i <= 12; i++)

            {

                if (Weekday.GetWeekday(1, i, year) == day)

                {

                    counter++;

                }

            }

​

            return counter;

        }

    }

}

​