GregorianCalendar add() Method in Java

The java.util.GregorianCalendar.add(int calendarfield, int time) is an in-built method of GregorianCalendar class in Java. The function accepts a calendar field and the amount of time to be added to that particular calendar field as a parameter. Based on the calendar rules, the method adds or deducts, based on its sign, the specified amount of time to the specified field. Syntax:

public void add(int calendarfield, int time)

Parameters: The function accepts two mandatory parameters which are described below:

• calendarfield: The calendar field which is to be modified.
• time : The amount of time to be added.

Return Values: This method has no return value. Exception: The method throws IllegalArgumentException if calendarfield has values ZONE_OFFSET, DST_OFFSET, or unknown, or if any of the calendar fields has an out-of-range value. Examples:

Current Date and Time : Mon Jul 23 12:46:05 UTC 2018

Input : calendarfield = GregorianCalendar.YEAR, time = 2
Output : Thu Jul 23 12:46:05 UTC 2020

Input : calendarfield = GregorianCalendar.MONTH, time = 16
Output : Sat Nov 23 12:46:45 UTC 2019

Below programs illustrate the use of java.util.GregorianCalendar.add() method in Java: Program 1:

Java

// Java Program to demonstrate add() method

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        // Creating a new calendar
        GregorianCalendar newcalendar = (GregorianCalendar)
                           GregorianCalendar.getInstance();

        // Display the current date and time
        System.out.println(" Current Date and Time : "
                           + newcalendar.getTime());
        // Adding two months to the current date
        newcalendar.add((GregorianCalendar.MONTH), 2);

        // Display the modified date and time
        System.out.println(" Modified Date and Time : "
                           + newcalendar.getTime());
    }
}

Output:

Current Date and Time : Fri Aug 03 11:48:38 UTC 2018
 Modified Date and Time : Wed Oct 03 11:48:38 UTC 2018

Program 2:

Java

// Java Program to demonstrate add() method
import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        // Creating a new calendar
        GregorianCalendar newcalendar = (GregorianCalendar)
                           GregorianCalendar.getInstance();

        // Display the current date and time
        System.out.println(" Current Date and Time : "
                           + newcalendar.getTime());
        // Adding twenty years to the current date
        newcalendar.add((GregorianCalendar.YEAR), 20);
        // Display the modified date and time
        System.out.println(" Modified Date and Time : "
                           + newcalendar.getTime());
    }
}

Output:

Current Date and Time : Fri Aug 03 11:48:40 UTC 2018
 Modified Date and Time : Tue Aug 03 11:48:40 UTC 2038

Program 3:

Java

// Java Program to illustrate
// GregorianCalendar.add()
// function

import java.io.*;
import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        // Creating a new calendar
        GregorianCalendar newcalendar = (GregorianCalendar)
                           GregorianCalendar.getInstance();

        // Display the current date and time
        System.out.println(" Current Date and Time : "
                           + newcalendar.getTime());
        // Deducting 16 months to the current date
        newcalendar.add((GregorianCalendar.MONTH), -16);
        // Display the modified date and time
        System.out.println(" Modified Date and Time : "
                           + newcalendar.getTime());

        // Deducting twelve years to the current date
        newcalendar.add((GregorianCalendar.MONTH), -12);
        // Display the modified date and time
        System.out.println(" Modified Date and Time : "
                           + newcalendar.getTime());
    }
}

Output:

Current Date and Time : Fri Aug 03 11:48:43 UTC 2018
 Modified Date and Time : Mon Apr 03 11:48:43 UTC 2017
 Modified Date and Time : Sun Apr 03 11:48:43 UTC 2016

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/GregorianCalendar.html#add()