Java Calculate Age from Date of Birth

In this Java tutorial, we learn how to calculate age of someone from with their birthday as a Date object in Java programming language.

How to calculate age from Date of birth in Java

In this first step, we create a new Java class named DateUtil, and implement the getAge(Date birthday) static method, this method to calculate the number of age based on a given Date object and current system Date as Java code below.

DateUtil.java

import java.util.Calendar;
import java.util.Date;

public class DateUtil {

    /**
     * This method to calculate number of age from given birthday Date value.
     * @param birthday the Date of birth
     * @return number of age
     */
    public static int getAge(Date birthday) {
        Calendar birthdayCalendar = Calendar.getInstance();
        birthdayCalendar.setTime(birthday);

        Calendar todayCalendar = Calendar.getInstance();
        int age = todayCalendar.get(Calendar.YEAR) - birthdayCalendar.get(Calendar.YEAR);

        return age;
    }

}

In the following example Java code, we learn how to use the above getAge(Date birthday) static method to calculate age from given Date object in Java program.

GetAgeFromDateExample.java

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class GetAgeFromDateExample {
    public static void main(String... args) throws ParseException {
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy/MM/dd");
        Date birthDate = simpleDateFormat.parse("1988/07/11");

        // Calculate Age from Date of Birth
        int age = DateUtil.getAge(birthDate);

        System.out.println("Today: " + new Date());
        System.out.println("Date of birth: " + birthDate);
        System.out.println("Age: " + age);
    }
}

The output as below.

Today: Thu Aug 18 22:51:21 ICT 2022
Date of birth: Mon Jul 11 00:00:00 ICT 1988
Age: 34

Happy Coding 😊

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