Java Calculate Age from LocalDateTime of Birth

Tags: Java LocalDateTime DateUtil

In this Java tutorial, we learn how to calculate someone’s age based on their birthday as a LocalDateTime object in Java programming language.

How to calculate age from LocalDateTime of birth in Java

At this first step, we create a new Java class named DateUtil, and implement a new static method named getAge(LocalDateTime birthday), in this method we calculate the number of age from a given LocalDateTime value and current system date then return age value as an integer value.

DateUtil.java 

import java.time.LocalDateTime;
import java.time.temporal.ChronoUnit;

public class DateUtil {

    /**
     * This method to calculate number of age from given birthday LocalDateTime value.
     * @param birthday the LocalDateTime of birth
     * @return number of age
     */
    public static int getAge(LocalDateTime birthday) {
        LocalDateTime today = LocalDateTime.now();
        int age = (int)ChronoUnit.YEARS.between(birthday, today);
        return age;
    }

}

In this following example Java code, we learn how to use the DateUtil class above to calculate number of age from given LocalDateTime value in Java program.

GetAgeFromLocalDateTimeExample.java 

import java.time.LocalDateTime;

public class GetAgeFromLocalDateTimeExample {
    public static void main(String... args) {
        LocalDateTime birthday = LocalDateTime.of(1988, 7, 11, 0, 0, 0);

        // Calculate Age from LocalDateTime of Birth
        int age = DateUtil.getAge(birthday);

        System.out.println("Today: " + LocalDateTime.now());
        System.out.println("LocalDateTime of birth: " + birthday);
        System.out.println("Age: " + age);
    }
}
The output as below. 
Today: 2022-08-18T23:53:29.223557900
LocalDateTime of birth: 1988-07-11T00:00
Age: 34

Happy Coding 😊

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