Calculate Age from Birth Date in Java Calculate Age from Birth Date in Java

Ashish Lahoti
Java
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In this quick tutorial, we’ll learn how to calculate the age in human-readable format in Java.

Requirement

We want to create a utility method in Java that calculates the age from birth date as of today in human-readable format i.e. in Years, Months, and Days.

These are few examples of expected age as of date 2024-01-01 from the given birth date:-

Birth Date As of date Age
2000-01-01 2024-01-01 24 Years
1990-05-01 2024-01-01 33 Years and 8 Months
1980-08-22 2024-01-01 43 Years, 4 Months and 10 Days

Let’s build a utility method to achieve this.

Date Utility Method

Let’s create a LocalDate Java utility method DateUtils.calculateAge(birthDate) to calculate age from the birth date as of today in human-readable format i.e. in Years, Months, and Days.

package com.example.util;

import java.time.LocalDate;
import java.time.Period;

public class DateUtils {

  public static String calculateAge(LocalDate birthDate) {
    return getDiffInHumanReadableFormat(birthDate, LocalDate.now());
  }

  public static String getDiffInHumanReadableFormat(LocalDate startDate, LocalDate endDate) {
    Period period = Period.between(startDate, endDate);
    StringBuilder token = new StringBuilder();
    appendUnits(token, period.getYears(), "Year");
    yearSeparator(period, token);
    appendUnits(token, period.getMonths(), "Month");
    monthSeparator(period, token);
    appendUnits(token, period.getDays(), "Day");
    return token.toString().trim();
  }

  private static void appendUnits(StringBuilder token, int units, String unitName) {
    if (units > 0) {
      token.append(units).append(" ").append(unitName);
      if (units > 1) token.append("s");
    }
  }

  private static void yearSeparator(Period period, StringBuilder token) {
    if (period.getYears() > 0 && period.getMonths() > 0) {
      token.append(period.getDays() > 0 ? ", " : " and ");
    }
  }

  private static void monthSeparator(Period period, StringBuilder token) {
    boolean appendAnd = (period.getMonths() > 0 && period.getDays() > 0) ||
            (period.getMonths() == 0 && period.getYears() > 0 && period.getDays() > 0);
    if (appendAnd) token.append(" and ");
  }
}

Let’s call the utility method to calculate Age:-

LocalDate birthDate = LocalDate.of(1980, 8, 22);
System.out.println("BirthDate: " + birthDate);
System.out.println("Age: " + calculateAge(birthDate));
//BirthDate: 1980-08-22
//Age: 43 Years, 4 Months and 13 Days

Please note that the Age calculation will be different depending on today’s date.

That’s it! You can copy the code and use it. Thanks for reading!