C# Program to Check if a Given Year is a Leap Year

This program provides a simple yet effective way to determine if a given year is a leap year in C#. It’s a fundamental concept that can be a starting point for more complex date-related applications.

Problem statement

Write a C# program that determines whether a given year is a leap year or not.

C# Program to Check if a Given Year is a Leap Year

using System;

class Program
{
    static void Main()
    {
        Console.Write("Enter a year: ");
        int year = int.Parse(Console.ReadLine());

        if (IsLeapYear(year))
        {
            Console.WriteLine(year + " is a leap year.");
        }
        else
        {
            Console.WriteLine(year + " is not a leap year.");
        }
    }

    static bool IsLeapYear(int year)
    {
        // A year is a leap year if it is divisible by 4, 
        // except for years that are divisible by 100 but not by 400.
        return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
    }
}

How it works

The C# program provided checks if a given year is a leap year. Let’s break down how it works step by step:

User Input:

• The program starts by prompting the user to enter a year.

Code:

Console.Write(“Enter a year: “);
int year = int.Parse(Console.ReadLine());

The Console.Write method displays the message “Enter a year: ” on the console, prompting the user to input a year. The Console.ReadLine method reads the input as a string, and int.Parse converts it to an integer, which is stored in the variable year.

Leap Year Check:

• The program then calls the IsLeapYear method to determine if the entered year is a leap year.

Code:

if (IsLeapYear(year))
{
Console.WriteLine(year + ” is a leap year.”);
}
else
{
Console.WriteLine(year + ” is not a leap year.”);
}

If the IsLeapYear method returns true, it prints a message indicating that the year is a leap year. Otherwise, it prints a message indicating that it is not.

IsLeapYear Method:

• This method contains the logic to determine if a year is a leap year.

Code:

static bool IsLeapYear(int year)
{
return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}

• The method takes an integer year as input and returns a boolean value (true if it’s a leap year, false if it’s not).
• The logic checks two conditions:
  • year % 4 == 0 && year % 100 != 0: This checks if the year is divisible by 4 but not divisible by 100. This is the general rule for leap years.
  • year % 400 == 0: This handles an exception to the general rule. If a year is divisible by 400, it is a leap year even if it’s also divisible by 100.

Output:

• Based on the result of the IsLeapYear method, the program prints an appropriate message indicating whether the year is a leap year or not.

Example Execution:

Let’s say the user inputs the year 2020. The program will execute as follows:

• User Input: 2020
• Leap Year Check (IsLeapYear(2020)):
  • (2020 % 4 == 0 && 2020 % 100 != 0) evaluates to true.
  • So, IsLeapYear(2020) returns true.
• Output: 2020 is a leap year.

The program will display this message on the console.

If the user inputs 1900, the program will execute differently:

• User Input: 1900
• Leap Year Check (IsLeapYear(1900)):
  • (1900 % 4 == 0 && 1900 % 100 != 0) evaluates to false.
  • So, IsLeapYear(1900) returns false.
• Output: 1900 is not a leap year.

This provides a clear indication of whether the entered year is a leap year or not.

Input/Output