in src/main/java/org/apache/commons/validator/DateValidator.java [69:92]
    public boolean isValid(final String value, final String datePattern, final boolean strict) {
        if (value == null
                || datePattern == null
                || datePattern.isEmpty()) {
            return false;
        }
        final SimpleDateFormat formatter = new SimpleDateFormat(datePattern);
        formatter.setLenient(false);
        try {
            formatter.parse(value);
        } catch (final ParseException e) {
            return false;
        }
        if (strict && (datePattern.length() != value.length())) {
            return false;
        }
        return true;
    }