输入某年某月某日，输出当天是星期几？

//输入年月日
        int year = Convert.ToInt32(Console.ReadLine());
        int month = Convert.ToInt32(Console.ReadLine());
        int day = Convert.ToInt32(Console.ReadLine());
        int sum = 0;
        int count = 0;//计数器
        for (int i = 1; i < year; i++)
        {
            //判断公元1年到输入年份的前一年是闰年仍是平年
            if (i % 4 == 0&&i%100!=0 || i % 400 == 0)//判断某年时闰年仍是平年的条件
            {
                sum = 366;
            }
            else
            {
                sum = 365;
            }
            for (int j = 1; j <= sum; j++)
            {
                count++;
                if (count==7)//count表示天数，七天一个循环，当count=7时，计数器归零，从新计数
                {
                    count = 0;
                }
            }
        }
        int[] toDay ;//定义数组存储一年每月的天数
        //判断输入的年份是闰年仍是平年
        if (year % 4 == 0&&year%100!=0 ||year % 400 == 0)
        {//闰年二月是29天
             toDay = new int[] { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        }
        else
        {//平年二月是28天
             toDay = new int[] { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        }
        int sum1 = 0;

        for (int i = 0; i < month-1; i++)
        {
            sum1 += toDay[i];
        }
        int sum2 = sum1 + day;//输入日期是当年的第几天
        for (int i = 1; i <= sum2; i++)
        {
            count++;
            if (count==7)
            {
                count = 0;
            }
        }
        switch (count)
        {
            case 1:
                Console.WriteLine("星期一");
                break;
            case 2:
                Console.WriteLine("星期二");
                break;
            case 3:
                Console.WriteLine("星期三");
                break;
            case 4:
                Console.WriteLine("星期四");
                break;
            case 5:
                Console.WriteLine("星期五");
                break;
            case 6:
                Console.WriteLine("星期六");
                break;
            case 0:
                Console.WriteLine("星期日");
                break;
            default:
                break;
        }