How to find the number of days in a month of a particular year in Java?

The given task is to find the number of days in a month of a particular year. To understand this, consider that if we can determine the maximum day value in a month, we can use that as the number of days in that month.

To do this, we can use the GregorianCalendar class. It is a concrete subclass of the Calendar class, and it provides the standard calendar system used by most of the world. In Java, this GregorianCalendar can handle both the Gregorian calendar as well as Julian calendar.

Following are the different ways to find the number of days in a month of a particular year:

• Using getActualMaximum() Method
• Using YearMonth Class

Number of Days in a Month using getActualMaximum()

This is one of the common ways to find the number of days in a month of a particular year is by using the getActualMaximum() method of the GregorianCalendar class. This method returns the highest value a specific calendar field can have. You can pass any field from the Calendar class as a parameter.

Syntax

Following is the syntax of the getActualMaximum() method:

public int getActualMaximum(int field)

Here, the field parameter refers to the calendar whose maximum value needs to be returned.

Example 1

In the following example, we use the getActualMaximum() method to find the maximum value (i.e., number of days) in a month of March of a particular year 2025, that the GregorianCalendar field can have:

import java.util.*;

public class NoOfDaysInAMonthOfAYearTest {
   public static void main(String[] args) {
      int year = 2025;
      System.out.println("Given year: " + year);
      
      // GregorianCalendar for March
      Calendar calendar = new GregorianCalendar(year, Calendar.MARCH, 1);
      
      // Using getActualMaximum() method
      int numberOfDays = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
      System.out.println("The number of days in 'March' in the year " + year + " is: " + numberOfDays);
   }
}

The above program displays the number of days in a 'March' in the year 2025:

Given year: 2025
The number of days in 'March' in the year 2025 is: 31

Example 2

The following is another example of how to find the number of days in February for each year from 2000 to 2017.

It uses a loop to go through each year in that range and the GregorianCalendar class, along with the getActualMaximum() method, to calculate the number of days in February for that specific year:

import java.util.*;

public class NoOfDaysInAMonthOfAYearTest {
   public static void main(String[] args) {
      System.out.println("Number of days in February from 2000 to 2017: ");
      
      // Loop through years from 2000 to 2017
      for (int year = 2000; year < 2018; year++) {
         // Create a GregorianCalendar for February
         Calendar calendar = new GregorianCalendar(year, Calendar.FEBRUARY, 1);
         
         // Get the actual maximum number of days in February
         int numberOfDays = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);
         
         System.out.println("February " + year + ": " + numberOfDays + " days");
      }
   }
}

The above program produces the following output:

Number of days in February from 2000 to 2017: 
February 2000: 29 days
February 2001: 28 days
February 2002: 28 days
February 2003: 28 days
February 2004: 29 days
February 2005: 28 days
February 2006: 28 days
February 2007: 28 days
February 2008: 29 days
February 2009: 28 days
February 2010: 28 days
February 2011: 28 days
February 2012: 29 days
February 2013: 28 days
February 2014: 28 days
February 2015: 28 days
February 2016: 29 days
February 2017: 28 days

Using YearMonth Class

Here is another way to find the number of days in a month of a particular year using the YearMonth class from java.time package. This class represents a specific year and month and provides a method called lengthOfMonth() to get the number of days in that month.

Syntax

Following is the syntax of the YearMonth class:

YearMonth ym = YearMonth.of(year, month);

Here,

• year: It is an integer representing the desired year.
• month: It is an integer from 1 (for January) to 12 (for December).

Example

This is another example of finding the number of days in a specific month, May of a particular year, 2025, using the Java YearMonth class from the java.time package. In this example, we use YearMonth.of(year, month) and lengthOfMonth() to get the total days:

import java.time.YearMonth;

public class DaysInMonthExample {
   public static void main(String[] args) {
      int year = 2025;
      int month = 5;
      System.out.println("The given year is: " + year);
      System.out.println("The given month is: " + month);
      
      YearMonth yearMonth = YearMonth.of(year, month);
      int daysInMonth = yearMonth.lengthOfMonth();
      
      System.out.println("Number of days in 'May' of year " + year + ": " + daysInMonth + " days");
   }
}

Following is the output of the above program:

The given year is: 2025
The given month is: 5
Number of days in 'May' of year 2025: 31 days