How to Calculate Date Difference in Java

In Java, date plays a very important role in calculating date differences. In designing the application, a date can be of joining an organization, admission date, appointment date etc. Many times we need to calculate the difference between two dates. There can be more than one reason for calculating the date difference.

In Java, there is more than one way of getting the difference between two dates, which are as follows:

By using the SimpleDateFormat and Date classes
By using the TimeUnit class
By using the Period class

How to Calculate Date Difference in Java

Let's understand all three ways, one by one and understand how all these three classes are used to calculate the date difference in Java.

SimpleDateFormat and Date classes

The SimpleDateFormat class is used for formatting and parsing the data. It is used to convert a date from one format into another format. In order to create a Date object of a given string date format, the SimpleDateFormat class is very helpful.

There are the following steps that we will use to find the date difference using SimpleDateFormat and Date classes.

1) Create an object

In the first step, we will create an instance of the SimpleDatFormat class and convert the string date format into a date object.

2) Parse date

We will use the parse() method of that class for parsing both the string date into date object format.

3) Using getTime() method

In the next step, we will get the difference between both the dates using the getTime() method. We will calculate the difference in milliseconds.

4) Use mathematical formula

We can also use the mathematical formula if we want to get the difference in terms of years, days, hours, minutes, and seconds.

5) Print result

At last, we will print the difference between both the dates.

Let's take an example to understand how we can implement the above steps:

DifferenceExample1.java

import java.text.SimpleDateFormat;
import java.text.ParseException; 
import java.util.Date; 
class DifferenceExample1 {   
    // Create function for finding difference 
    static void find(String join_date, String leave_date) 
    { 
        // Create an instance of the SimpleDateFormat class
        SimpleDateFormat obj = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss"); 
        // In the try block, we will try to find the difference
        try { 
			// Use parse method to get date object of both dates
            Date date1 = obj.parse(join_date); 
            Date date2 = obj.parse(leave_date); 
            // Calucalte time difference in milliseconds 
            long time_difference = date2.getTime() - date1.getTime();
			// Calucalte time difference in days
            long days_difference = (time_difference / (1000*60*60*24)) % 365; 
			// Calucalte time difference in years
            long years_difference = (time_difference / (1000l*60*60*24*365)); 
			// Calucalte time difference in seconds
            long seconds_difference = (time_difference / 1000)% 60; 
			// Calucalte time difference in minutes
            long minutes_difference = (time_difference / (1000*60)) % 60; 
			
			// Calucalte time difference in hours
            long hours_difference = (time_difference / (1000*60*60)) % 24; 
			// Show difference in years, in days, hours, minutes, and seconds 
            System.out.print( 
                "Difference "
                + "between two dates is: "); 
            System.out.println( 
                hours_difference 
                + " hours, "
                + minutes_difference 
                + " minutes, "
                + seconds_difference 
                + " seconds, "
				+ years_difference 
                + " years, "
                + days_difference 
                + " days"
				); 
        } 
        // Catch parse exception 
        catch (ParseException excep) { 
            excep.printStackTrace(); 
        } 
    } 
    // Main class
    public static void main(String[] args) 
    { 
        // Set values for both dates
        String join = "12-12-2018 02:11:20"; 
        String leave  = "1-26-2020 07:15:50"; 
        // Calling find() method for getting difference bwtween dates
        find(join, leave); 
    } 
}

Output:

TimeUnit class

Java provides the best way of finding the date difference, i.e., TimeUnit class. The process of finding the difference between the two dates is the same as using the SimpleDateFormatClass. The only difference is that we use the TimeUnit built-in class and its methods like toSeconds(), toMinutes(), toHours(), and toDays(). These methods directly return the days, hours, minutes and seconds.

Let's take an example to understand how the TimeUnit class is used to get the date difference.

DifferenceExample2.java

import java.text.SimpleDateFormat;
import java.util.concurrent.TimeUnit; 
import java.text.ParseException; 
import java.util.Date; 
class DifferenceExample2 { 
    // Create function for finding difference 
    static void find(String join_date, String leave_date) 
    { 
        // Create an instance of the SimpleDateFormat class
        SimpleDateFormat obj = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss"); 
  
        // In the try block, we will try to find the difference
        try { 
			
			// Use parse method to get date object of both dates
            Date date1 = obj.parse(join_date); 
            Date date2 = obj.parse(leave_date); 
  
            // Calucalte time difference in milliseconds 
            long time_difference = date2.getTime() - date1.getTime();
			
			// Calucalte time difference in days using TimeUnit class
            long days_difference = TimeUnit.MILLISECONDS.toDays(time_difference) % 365;
			
			// Calculate time difference in years using TimeUnit class
            long years_difference = TimeUnit.MILLISECONDS.toDays(time_difference) / 365l;
			// Calucalte time difference in seconds using TimeUnit class
            long seconds_difference = TimeUnit.MILLISECONDS.toSeconds(time_difference) % 60;
			// Calucalte time difference in minutes using TimeUnit class
            long minutes_difference = TimeUnit.MILLISECONDS.toMinutes(time_difference) % 60; 
			// Calucalte time difference in hours using TimeUnit class
            long hours_difference = TimeUnit.MILLISECONDS.toHours(time_difference) % 24; 
			// Show difference in years, in days, hours, minutes, and seconds 
            System.out.print( 
                "Difference "
                + "between two dates is: "); 
            System.out.println( 
                hours_difference 
                + " hours, "
                + minutes_difference 
                + " minutes, "
                + seconds_difference 
                + " seconds, "
				+ years_difference 
                + " years, "
                + days_difference 
                + " days"
				); 
        } 
        // Catch parse exception 
        catch (ParseException excep) { 
            excep.printStackTrace(); 
        } 
    } 
    // Main class
    public static void main(String[] args) 
    { 
        // Set values for both dates
        String join = "12-12-2018 02:11:20"; 
        String leave  = "1-26-2020 07:15:50"; 
  
        // Calling find() function for getting difference bwtween dates
        find(join, leave); 
    } 
}

Output:

Period class

Java provides another important built-in class that is very helpful to find the difference between the two days. We use the Period class to find the difference in terms of days, months and years. The Period class is similar to the TimeUnit class. The period class's between() method is responsible for calculating the difference between dates. The Period class provides several methods like ofYears(), withMonths(), withYears(), withDays(), toTotalMonths(), ofDays(), ofWeeks(), and ofMonths() etc.

Let's take an example to understand how the period class between() method is used to get the date difference in days, months, and years.

DifferenceExample3.java

import java.time.*; 
import java.util.*; 
class DifferenceExample3 { 
    // Create function for finding difference 
    static void find(LocalDate  first_date, LocalDate second_date) 
    { 
        // Get period between the first and the second date 
        Period difference = Period.between(first_date, second_date); 
        // Show date difference in years, months, and days 
        System.out.print("Difference between two dates is:\n"); 
        System.out.printf( "%d days, %d months and %d years", 
            difference.getDays(),
			difference.getMonths(), 
			difference.getYears()); 
    } 
    // Main class
    public static void main(String[] args) 
    { 
        // Create first and second date using LocalDate's of() method
        LocalDate first_date = LocalDate.of(1997, 02, 15); 
		LocalDate second_date = LocalDate.of(2016, 03, 22); 
        // Calling find() method to get and print the period between both dates 
        find(first_date, second_date); 
    } 
}

Output:

The above three methods are commonly used ways for getting the date difference in Java. The SimpleDateFormat class is the simplest way of getting the date difference in terms of days, months and years.

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