[Jumpstart C#] Conditional statements - Valid date ?

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

namespace _6.Valid_date_or_invalid_date
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.Write("day = ");
            int day = Int32.Parse(Console.ReadLine());
            Console.Write("month = ");
            int month = Int32.Parse(Console.ReadLine());
            Console.Write("year = ");
            int year = Int32.Parse(Console.ReadLine());

            int lastDayOfTheMotnth =31 ;

            //if (month == 4 || month == 6 || month == 9 || month == 11)
            //{
            //    lastDayOfTheMotnth = 30;
            //}
            //else if (month == 2)
            //{
            //    bool isLeapYear = year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
            //    lastDayOfTheMotnth = isLeapYear ? 29 : 28;
            //}   //работи по-бавно

            switch (month)
            {
                case 4:
                case 6:
                case 9:
                case 11:
                    lastDayOfTheMotnth = 30;
                    break;
                case 2:
                    bool isLeapYear = year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);
                    lastDayOfTheMotnth = isLeapYear ? 29 : 28;
                    break;
            }  // switch работи по-бързо

            if (year >= 1  && day >= 1 &&
               month >=1 && month <= 12 &&
               day <= lastDayOfTheMotnth)
                Console.WriteLine("Valid date");
            else
                Console.WriteLine("Invalid date");
        }
    }
}