GregorianCalendar equals() Method in Java

The java.util.GregorianCalendar.equals() method is an in-built function in Java which checks for equality between this GregorianCalendar instance and the Object passed as parameter to the function. It returns true only if the specified Object is a GregorianCalendar object with same time value (millisecond offset from the Epoch) as this GregorianCalendar instance.

Syntax:

public boolean equals(Object obj)

Parameters: The function accepts a single mandatory parameter obj which is to be compared with this GregorianCalendar instance.

Return Values: This method returns true only when the specified Object is a GregorianCalendar object and has the same time value (millisecond offset from the Epoch) as this instance and returns false otherwise.

Examples:

Input : c1 = Mon Jul 23 23:46:14 UTC 2018, c2 = Mon Jul 23 23:46:14 UTC 2018
Output : true

Input : c1 = Mon Jul 23 23:46:14 UTC 2018, c2 = Sun Jul 24 00:02:52 UTC 2022
Output : false

Below programs illustrate the java.util.GregorianCalendar.equals() function: 

Program 1:

Java

// Java Program to illustrate the equals() function
// of GregorianCalendar class

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

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

        // Create a new calendar
        GregorianCalendar c1 = (GregorianCalendar)
                     GregorianCalendar.getInstance();

        // Display the current date and time
        System.out.println("Current Date and Time : "
                           + c1.getTime());

        // Create a second calendar equal to first one
        GregorianCalendar c2 =
              (GregorianCalendar)(Calendar)c1.clone();

        // Compare the two calendars
        System.out.println("Both calendars are equal:"
                           + c1.equals(c2));

        // Adding 15 months to second calendar
        c2.add(GregorianCalendar.MONTH, 15);

        // Display the current date and time
        System.out.println("Modified Date and Time : "
                           + c2.getTime());

        // Compare the two calendars
        System.out.println("Both calendars are equal:"
                           + c1.equals(c2));
    }
}

Output:

Current Date and Time : Fri Jul 27 12:05:05 UTC 2018
Both calendars are equal:true
Modified Date and Time : Sun Oct 27 12:05:05 UTC 2019
Both calendars are equal:false

Program 2:

Java

// Java Program to illustrate the equals() function
// of GregorianCalendar class

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

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

        // Create a new calendar
        GregorianCalendar c1 = (GregorianCalendar)
                     GregorianCalendar.getInstance();

        // Display the current date and time
        System.out.println("Current Date and Time : "
                           + c1.getTime());

        // Create a second calendar equal to first one
        GregorianCalendar c2 =
             (GregorianCalendar)(Calendar)c1.clone();

        // Compare the two calendars
        System.out.println("Both calendars are equal:"
                           + c1.equals(c2));

        // Changing the Time Zone of c2
        c2.setTimeZone(TimeZone.getTimeZone("CST"));

        // Compare the two calendars
        System.out.println("Both calendars are equal:"
                           + c1.equals(c2));
    }
}

Output:

Current Date and Time : Fri Jul 27 12:05:08 UTC 2018
Both calendars are equal:true
Both calendars are equal:false

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