Java Month Enum

Last modified: April 16, 2025

The java.time.Month enum represents the twelve months of the year. It is part of the Java Date and Time API introduced in Java 8. Each enum constant provides useful methods for working with months.

Month is immutable and thread-safe. It provides methods to get month names, lengths, and values. The enum works seamlessly with other date-time classes like LocalDate and YearMonth.

Month Enum Overview

The Month enum contains twelve constants from JANUARY to DECEMBER. Each constant has methods to query month properties and perform conversions. The enum follows the ISO-8601 calendar system.

public enum Month implements TemporalAccessor, TemporalAdjuster { JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER;

public int getValue();
public String getDisplayName(TextStyle style, Locale locale);
public int length(boolean leapYear);
public int minLength();
public int maxLength();
public Month firstMonthOfQuarter();
public Month plus(long months);
public Month minus(long months);

}

The code above shows the structure and key methods of the Month enum. These methods allow querying month properties and performing calculations. The enum provides both numerical and textual representations of months.

Getting Month Values

Each Month constant has a numerical value from 1 (January) to 12 (December). The getValue method returns this value. This is useful for compatibility with older APIs that use month numbers.

Main.java

package com.zetcode;

import java.time.Month;

public class Main {

public static void main(String[] args) {
    
    // Get month values
    System.out.println("January value: " + Month.JANUARY.getValue());
    System.out.println("December value: " + Month.DECEMBER.getValue());
    
    // Get month from value
    Month month = Month.of(6);
    System.out.println("Month 6: " + month);
    
    // Get current month
    Month current = Month.from(java.time.LocalDate.now());
    System.out.println("Current month: " + current);
}

}

This example demonstrates basic operations with Month values. The of method creates a Month from its numerical value. The from method extracts Month from other date-time objects.

Displaying Month Names

The getDisplayName method provides localized month names in various text styles. This is useful for user interfaces that need to display month names in different formats and languages.

Main.java

package com.zetcode;

import java.time.Month; import java.time.format.TextStyle; import java.util.Locale;

public class Main {

public static void main(String[] args) {
    
    // Full name in English
    String fullName = Month.AUGUST.getDisplayName(
        TextStyle.FULL, Locale.ENGLISH);
    System.out.println("Full name: " + fullName);
    
    // Short name in French
    String shortName = Month.AUGUST.getDisplayName(
        TextStyle.SHORT, Locale.FRENCH);
    System.out.println("Short name in French: " + shortName);
    
    // Narrow name in German
    String narrowName = Month.AUGUST.getDisplayName(
        TextStyle.NARROW, Locale.GERMAN);
    System.out.println("Narrow name in German: " + narrowName);
}

}

This example shows different ways to display month names. The TextStyle enum controls the name format (FULL, SHORT, NARROW). The Locale parameter provides localization support.

Working with Month Lengths

The Month enum provides methods to query month lengths. These methods are essential for date calculations and validation. February’s length depends on whether it’s a leap year.

Main.java

package com.zetcode;

import java.time.Month;

public class Main {

public static void main(String[] args) {
    
    // Regular month lengths
    System.out.println("January days: " + Month.JANUARY.length(false));
    System.out.println("April days: " + Month.APRIL.length(false));
    
    // February in leap year
    System.out.println("February in leap year: " + 
        Month.FEBRUARY.length(true));
        
    // Min and max lengths
    System.out.println("February min days: " + 
        Month.FEBRUARY.minLength());
    System.out.println("February max days: " + 
        Month.FEBRUARY.maxLength());
}

}

This example demonstrates month length queries. Most months have fixed lengths, but February varies. The minLength and maxLength methods provide bounds for February’s length.

Month Arithmetic

The Month enum supports arithmetic operations through plus and minus methods. These operations wrap around at year boundaries, making them useful for month-based calculations.

Main.java

package com.zetcode;

import java.time.Month;

public class Main {

public static void main(String[] args) {
    
    // Basic arithmetic
    Month nextMonth = Month.JANUARY.plus(1);
    System.out.println("January + 1: " + nextMonth);
    
    Month prevMonth = Month.JANUARY.minus(1);
    System.out.println("January - 1: " + prevMonth);
    
    // Wrapping around year boundary
    Month decPlus2 = Month.DECEMBER.plus(2);
    System.out.println("December + 2: " + decPlus2);
    
    Month janMinus3 = Month.JANUARY.minus(3);
    System.out.println("January - 3: " + janMinus3);
    
    // Large values
    Month janPlus25 = Month.JANUARY.plus(25);
    System.out.println("January + 25: " + janPlus25);
}

}

This example shows month arithmetic operations. The calculations automatically wrap around at year boundaries. Adding 1 to December gives January, and subtracting 1 from January gives December.

Working with Quarters

The firstMonthOfQuarter method returns the first month of each quarter. This is useful for financial and business applications that organize time by quarters.

Main.java

package com.zetcode;

import java.time.Month;

public class Main {

public static void main(String[] args) {
    
    // Get first month of quarters
    System.out.println("Q1 starts with: " + 
        Month.JANUARY.firstMonthOfQuarter());
    System.out.println("Q2 starts with: " + 
        Month.APRIL.firstMonthOfQuarter());
    System.out.println("Q3 starts with: " + 
        Month.JULY.firstMonthOfQuarter());
    System.out.println("Q4 starts with: " + 
        Month.OCTOBER.firstMonthOfQuarter());
        
    // Any month in quarter returns same result
    System.out.println("May's quarter starts with: " + 
        Month.MAY.firstMonthOfQuarter());
}

}

This example demonstrates quarter-related operations. Each quarter consists of three months, and the method returns the first month regardless of which month in the quarter is used to call it.

Using Month with LocalDate

The Month enum works seamlessly with LocalDate. This combination is powerful for date manipulation and querying. The examples show common operations between these classes.

Main.java

package com.zetcode;

import java.time.LocalDate; import java.time.Month; import java.time.Year;

public class Main {

public static void main(String[] args) {
    
    // Create date with Month enum
    LocalDate date1 = LocalDate.of(2025, Month.JANUARY, 15);
    System.out.println("Date with Month enum: " + date1);
    
    // Get month from date
    Month month = date1.getMonth();
    System.out.println("Month from date: " + month);
    
    // Create date at start of month
    LocalDate startOfMonth = Year.now().atMonth(Month.MARCH).atDay(1);
    System.out.println("Start of March: " + startOfMonth);
    
    // Check if month has 31 days
    boolean has31Days = month.maxLength() == 31;
    System.out.println(month + " has 31 days: " + has31Days);
}

}

This example shows integration between Month and LocalDate. The Month enum provides type safety when creating dates. The example also demonstrates querying month properties from dates.

Source

Java Month Enum Documentation

In this article, we’ve covered the essential methods and features of the Java Month enum. Understanding these concepts is crucial for date handling in modern Java applications.

Author

My name is Jan Bodnar, and I am a dedicated programmer with many years of experience in the field. I began writing programming articles in 2007 and have since authored over 1,400 articles and eight e-books. With more than eight years of teaching experience, I am committed to sharing my knowledge and helping others master programming concepts.

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