Hackerrank - week of code - day of programmer -

DayOfProgrammer.cs

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

namespace DayOfProgrammer
{
    class Program
    {
        static void Main(string[] args)
        {
            int year = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine(CalculateDayOfProgrammer(year)); 
        }

        public static string CalculateDayOfProgrammer(int year)
        {
            int start = 1700;            

            bool isJulianCalendar    = year >= start && year <= 1917;
            bool isGregorianCalendar = year >= 1919;
            int[] daysInFirst8Months = new int[] {31,28,31,30,31,30,31,31};

            int offDaysInFeb = 0; 
            if(year == 1998)
            {
                offDaysInFeb = 13;
            }

            if(isJulianCalendar && year % 4 ==0)
            {
                daysInFirst8Months[1] = 29; 
            }

            if(isGregorianCalendar && (year % 400 == 0 || (year % 4 == 0 && year % 100 > 0)))
            {
                daysInFirst8Months[1] = 29; 
            }

            daysInFirst8Months[1] -= offDaysInFeb;

            int theDayOfSept = 256 - daysInFirst8Months.Sum(); 
            
            return theDayOfSept + ".09." + year;                       
        }
    }
}