Calculate age in Java

public static int getAge(long dateOfBirth) {
        Calendar today = Calendar.getInstance();
        Calendar birthDate = Calendar.getInstance();

        int age = 0;

        birthDate.setTimeInMillis(dateOfBirth);
        if (birthDate.after(today)) {
            return -1;
        }

        age = today.get(Calendar.YEAR) - birthDate.get(Calendar.YEAR);

        // If birth date is greater than todays date (after 2 days adjustment of
        // leap year) then decrement age one year
        if ((birthDate.get(Calendar.DAY_OF_YEAR)
                - today.get(Calendar.DAY_OF_YEAR) > 3)
                || (birthDate.get(Calendar.MONTH) > today.get(Calendar.MONTH))) {
            age--;

            // If birth date and todays date are of same month and birth day of
            // month is greater than todays day of month then decrement age
        } else if ((birthDate.get(Calendar.MONTH) == today.get(Calendar.MONTH))
                && (birthDate.get(Calendar.DAY_OF_MONTH) > today
                        .get(Calendar.DAY_OF_MONTH))) {
            age--;
        }

        return age;
    }