Get age from a birthday date

import java.util.Date;

public class Main {
  public static final long MILLIS_PER_DAY = 1000 * 60 * 60 * 24;
  public static final long MILLIS_PER_YEAR = 365 * MILLIS_PER_DAY;

  public static int getAge(Date birthDate) {
    if (birthDate == null)
      return 0;
    long ageMillis = System.currentTimeMillis() - birthDate.getTime();
    return (int) (ageMillis / MILLIS_PER_YEAR);
  }
}

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

public class DateHelper {
  public static float getAge(final Date birthdate) {
    return getAge(Calendar.getInstance().getTime(), birthdate);
  }

  public static float getAge(final Date current, final Date birthdate) {

    if (birthdate == null) {
      return 0;
    }
    if (current == null) {
      return getAge(birthdate);
    } else {
      final Calendar calend = new GregorianCalendar();
      calend.set(Calendar.HOUR_OF_DAY, 0);
      calend.set(Calendar.MINUTE, 0);
      calend.set(Calendar.SECOND, 0);
      calend.set(Calendar.MILLISECOND, 0);

      calend.setTimeInMillis(current.getTime() - birthdate.getTime());

      float result = 0;
      result = calend.get(Calendar.YEAR) - 1970;
      result += (float) calend.get(Calendar.MONTH) / (float) 12;
      return result;
    }

  }
}