.NET Program to check Leap Year or Not

Introduction

According to Wikipedia, Leap year is a year containing one additional day in order to keep the calendar year synchronized with seasonal year.

Conditions to call year as leap year:

Condition1: Divisible by 400. For example: 1200,1600, 2000 are leap years.

Condition2: Not divisible by 400 and 100 but Divisible by 4. For example: 2002, 2008,2012,2016 are leap years.

Using the above 2 conditions, we will write a program to check whether user input year is leap year or not.

Program:

namespace DotNetMirror
{
    class ClsIsLeapYear
    {
        private static void Main(string[] args)
        {
            int year;
            Console.Write("Enter any year:");
            year = Convert.ToInt32(Console.ReadLine());
            if (FnIsLeapYear(year)) //if ((year % 4 == 0) && (year % 400 == 0 || year % 100 != 0))
            {
                Console.WriteLine("{0} is a leap year.", year);
            }
            else
            {
                Console.WriteLine("{0} is not a leap year.", year);
            }
            Console.ReadLine();
        }
        public static bool FnIsLeapYear(int year)
        {
            if (year % 4 != 0) //400 and 100 divisible by 4 So check for not condition first
            {
                return false; //Not divisible by 4
            }
            else if (year % 400 == 0)
            {
                return true; //divisible by 400 (condition 1)
            }
            else if (year % 100 == 0)
            {
                return false; //divisible by 100
            }
            else
            {
                return true; //Not divisible by 400 and 100 but Divisible by 4 (Condition 2)
            }
        }
    }
}

If you feel FnIsLeapYear method implementation is bit difficult to understand, you can use simpler condition like 

if ((year % 4 == 0) && (year % 400 == 0 || year % 100 != 0)) 

Program Output: