Java Calculate Age from ZonedDateTime of Birth

Tags: Java ZonedDateTime DateUtil

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

How to calculate age from ZonedDateTime of birth in Java

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

DateUtil.java 

import java.time.ZonedDateTime;
import java.time.temporal.ChronoUnit;

public class DateUtil {

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

}

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

GetAgeFromZonedDateTimeExample.java 

import java.time.ZonedDateTime;

public class GetAgeFromZonedDateTimeExample {
    public static void main(String... args) {
        ZonedDateTime birthday = ZonedDateTime.parse("1988-07-11T00:00:00.00+07:00[Asia/Bangkok]");

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

        System.out.println("Today: " + ZonedDateTime.now());
        System.out.println("ZonedDateTime of birth: " + birthday);
        System.out.println("Age: " + age);
    }
}
The output as below. 
Today: 2022-08-19T00:05:06.483218300+07:00[Asia/Bangkok]
ZonedDateTime of birth: 1988-07-11T00:00+07:00[Asia/Bangkok]
Age: 34

Happy Coding 😊

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