Calculate the age of a person in Android Java

There are several ways to do the calculation. Here are two of them:

• java.time.chrono.ChronoPeriod

  The java.time package can be used from the API level 26. Example:

  Code:

  DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd", 
          Locale.getDefault());
  ChronoLocalDate from = ChronoLocalDate.from(formatter.parse("1989-10-10"));
  ChronoLocalDate to = ChronoLocalDate.from(formatter.parse("2017-09-29"));
  ChronoPeriod period = ChronoPeriod.between(from, to);
  
  Formatter fmt = new Formatter();
  if (period.get(ChronoUnit.YEARS) > 0) {
      fmt.format("%d años ", period.get(ChronoUnit.YEARS));
  }
  if (period.get(ChronoUnit.MONTHS) > 0) {
      fmt.format("%d meses ", period.get(ChronoUnit.MONTHS));
  }
  if (period.get(ChronoUnit.DAYS) > 0) {
      fmt.format("%d días ", period.get(ChronoUnit.DAYS));
  }
  System.out.println(fmt.toString());
  

  Exit:

  27 años 11 meses 19 días 
  

• java.util.GregorianCalendar

  You can also use java.util.GregorianCalendar , although it is not as accurate:

  Code:

  DateFormat dateFormat = dateFormat = new SimpleDateFormat("yyyy-MM-dd", 
          Locale.getDefault());
  Date dob = dateFormat.parse("1989-10-10");
  GregorianCalendar cal = (GregorianCalendar) Calendar.getInstance();
  cal.setGregorianChange(new Date(Long.MIN_VALUE));
  cal.clear();
  cal.set(Calendar.YEAR, 0);
  cal.setTimeInMillis( cal.getTimeInMillis() + new Date().getTime() - dob.getTime());
  
  Formatter fmtr = new Formatter();
  if (cal.get(Calendar.YEAR) > 0) {
      fmtr.format("%d años ", cal.get(Calendar.YEAR));
  }
  if (cal.get(Calendar.MONTH) > 0) {
      fmtr.format("%d meses ", cal.get(Calendar.MONTH));
  }
  if (cal.get(Calendar.DAY_OF_MONTH) > 0) {
      fmtr.format("%d días ", cal.get(Calendar.DAY_OF_MONTH));
  }
  System.out.println(fmtr.toString());
  

  Exit:

  27 años 11 meses 21 días 
  

One method would be to apply the format "yyyyMMdd" to the date of birth and current, a subtraction is made and divided by 1000, this way we can obtain the number of years, for this you can perform a method:

public  int getEdad(Date fechaNacimiento, Date fechaActual) {
    DateFormat formatter = new SimpleDateFormat("yyyyMMdd");
    int dIni = Integer.parseInt(formatter.format(fechaNacimiento));
    int dEnd = Integer.parseInt(formatter.format(fechaActual));
    int age = (dEnd-dIni)/10000;
    return age;
}

and apply it in this way, using the date of birth "1989-10-10":

   try {
            DateFormat dateFormat = dateFormat = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
            Date fechaNacimiento = dateFormat.parse("1989-10-10");
            Calendar cal = Calendar.getInstance();
            Date fechaActual = cal.getTime();

            System.out.println("Edad : " + String.valueOf(getEdad(fechaNacimiento, fechaActual)));

        } catch (ParseException e) {
            e.printStackTrace();
        }

having as output:

Edad : 27