using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleCalendar
{
    class Program
    {
        /// <summary>
        /// 判斷指定年份是不是閏年
        /// </summary>
        /// <param name="year">接收的年份</param>
        /// <returns>是閏年時，返回true</returns>
 

        static bool IsLeap(int year)
        {
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
                return true;
            return false;
        }
        /// <summary>
        /// 得到某年某月的天數
        /// </summary>
        /// <param name="year">接收的年份</param>
 

        /// <param name="month">接收的月份</param>
        /// <returns>返回天數</returns>
        static int GetDaysOfMonth(int year, int month)
        {
            if (month == 2)
            {
                if (IsLeap(year))
                    return 29;
                return 28;
            }
            
 
else if (month <= 7 && month % 2 != 0 || month > 7 && month % 2 == 0)
                return 31;
            return 30;
        }
        /// <summary>
        /// 計算某一年總共的天數
        /// </summary>
        /// <param name="year">接收的年份</param>
        /// <returns>返回天數</returns>
        static int GetDaysOfYear(int year)
        {
            if (IsLeap(year))
                return 366;
            return 365;
        }
        /// <summary>
        /// 根據提供的年月日，計算是這一年的第幾天
        /// </summary>
        /// <param name="year">接收的年份</param>
        /// <param name="month">接收的月份</param>
        /// <param name="day">第幾天</param>
        /// <returns>返回是這一年的第幾天</returns>
        static int GetDaysInYear(int year, int month, int day)
        {
            int inAllDays = 0;
            for (int i = 1; i <= month-1; i++)
                inAllDays += GetDaysOfMonth(year,i);
            return inAllDays + day;
        }
        /// <summary>
        /// 根據提供的年月日，計算從1900年1月1號，到這一天經過的總天數
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        /// <returns>返回總天數</returns>
        static int GetCrossDaysFrom1900(int year, int month, int day)
        {
            int allYearDays = 0;
            for (int i = 1900; i <= year-1; i++)
                allYearDays += GetDaysOfYear(i);
            return allYearDays + GetDaysInYear(year, month, day)-1;
        }
        /// <summary>
        /// 計算某年某月某日是星期幾
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        /// <returns></returns>
        static int GetDayOfWeek(int year, int month, int day)
        {
            int daysFrom1900=GetCrossDaysFrom1900(year, month, day);
            int week = daysFrom1900 % 7 + 1;
            return week;
        }
        /// <summary>
        /// 得到用戶輸入的年份
        /// </summary>
        /// <returns>返回輸入的年份</returns>
        static int GetUserInputYear()
        {
            Console.Write("請輸入一個年份：");
            while (true)
            {
                int year = int.Parse(Console.ReadLine());
                if (year < 1900 || year > 2100)
                    Console.Write("輸入有誤，請重新輸入：");
                else
                    return year;
            }
        }
        /// <summary>
        /// 得到用戶輸入的月份
        /// </summary>
        /// <returns>返回輸入的月份</returns>
        static int GetUserInputMonth()
        {
            Console.Write("請輸入一個月份：");
            while (true)
            {
                int month = int.Parse(Console.ReadLine());
                if (month < 1 || month > 12)
                    Console.Write("輸入有誤，請重新輸入：");
                else
                    return month;
            }
        }
        /// <summary>
        /// 打印日歷
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        static void PrintCalendar(int year,int month)
        {
            List<string> calendar = new List<string>();
            int daysFrom1900 = GetCrossDaysFrom1900(year, month, 1);
            int space = daysFrom1900 % 7;
            for (int i = 0; i < space; i++)
                calendar.Add("");
            for (int i = 1; i <= GetDaysOfMonth(year, month); i++)
                calendar.Add(i.ToString());
            Console.WriteLine("**************************************************");
            Console.WriteLine("一\t二\t三\t四\t五\t六\t日");
            for (int i = 0; i < calendar.Count; i++)
            {
                if (i % 7 == 0 && i != 0)
                    Console.WriteLine();
                Console.Write(calendar[i]+"\t");
            }
            Console.WriteLine();
            Console.WriteLine("**************************************************");           
        }

        static void Main(string[] args)
        {
            PrintCalendar(GetUserInputYear(), GetUserInputMonth());
            Console.ReadLine();
        }
    }
}

C# 通過各個函數實現控制臺日歷