C#万年历

class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("请输入年份：");
            int year = int.Parse(Console.ReadLine());
            Console.WriteLine("请输入月份：");
            int month = int.Parse(Console.ReadLine());
            int totaldays = GetTotaldays(year, month);
            Console.WriteLine("{0}年{1}月距离1900年1月1日共{2}天",year,month,totaldays);
            //打印万年历
            Console.WriteLine("星期日\t星期一\t星期二\t星期三\t星期四\t星期五\t星期六");
            //计算当月的第一天是星期几
            int week = totaldays % 7 + 1;
            if (week==7)//7代表周日
            {
                week = 0;//输出0个\t
            }
            for (int i = 1; i <= week; i++)//周日不输出，是周几输出几个\t
            {
                Console.Write("\t");
            }
            //获取当月天数，循环输出
            for (int i = 1; i <= GetMonthdays(year,month); i++)
            {
                Console.Write(i+"\t");
                if ((totaldays+i)%7==6)//逢周六换行
                {
                    Console.WriteLine();
                }
            }
            Console.ReadLine();//阻断控制台关闭
        }

        /// <summary>
        /// 获取总天数
        /// </summary>
        /// <param name="year">年份</param>
        /// <param name="month">月份</param>
        /// <returns>返回总天数</returns>
        private static int GetTotaldays(int year, int month)
        {
            int totaldays = 0;
            for (int i = 1900; i < year; i++)
            {
                totaldays += GetYeardays(i);
            }
            for (int j = 1; j < month; j++)
            {
                totaldays += GetMonthdays(year, j);
            }
            return totaldays;
        }
        /// <summary>
        /// 获取指定年中月拥有的天数
        /// </summary>
        /// <param name="year">年份</param>
        /// <param name="month">月份</param>
        /// <returns>月天数</returns>
        private static int GetMonthdays(int year, int month)
        {
            switch (month)
            {
                case 4:
                case 6:
                case 9:
                case 11:
                    return 30;
                case 2:
                    if (IsRun(year))
                    {
                        return 29;
                    }
                    else
                    {
                        return 28;
                    }
                default:
                    return 31;
            }
        }
        /// <summary>
        /// 判断是否为闰年
        /// </summary>
        /// <param name="year">年份</param>
        /// <returns>是否为闰年</returns>
        private static bool IsRun(int year)
        {
            bool Isrun;
            if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
            {
                Isrun = true;
            }
            else
            {
                Isrun = false;
            }
            return Isrun;
        }

        /// <summary>
        /// 获取指定年份的天数
        /// </summary>
        /// <param name="year">年份</param>
        /// <returns>年天数</returns>
        private static int GetYeardays(int year)
        {
            int yeardays;
            if (IsRun(year))
            {
                yeardays = 366;
            }
            else
            {
                yeardays = 365;
            }
            return yeardays;
        }
    }

效果如图: