How to calculate age?

I offten have on my projects a lot of conditions, which depends on the age of the client, user, his wife or dog ;-).

Standard Java API is not very friendly for this use case. If you can't use JodaTime as me, I hope you appreciate this little calculator.

public class AgeCalculator {

    public static int getAge(final Date dayOfBirth) {
        return getAge(dayOfBirth, new Date());
    }

    public static int getAge(final Date dayOfBirth, final Date referenceDay) {
        if (dayOfBirth == null) {
            throw new IllegalArgumentException("Parameter 'dayOfBirth' can't be null.");
        }
        if (referenceDay == null) {
            throw new IllegalArgumentException("Parameter 'referenceDay' can't be null.");
        }

        final Calendar calRef = Calendar.getInstance();
        calRef.setTime(referenceDay);

        final Calendar cal = Calendar.getInstance();
        cal.setTime(dayOfBirth);

        final int yearRef = calRef.get(Calendar.YEAR);

        final int year = cal.get(Calendar.YEAR);

        int result = yearRef - year;

        cal.set(Calendar.YEAR, yearRef);
        if (calRef.before(cal)) {
            result--;
        }

        return result;
    }

}