The paper analyzes the central verbal categories: tense and aspect in Polish Penal Code of 1997 against the background of other codes in Polish, the current Russian, Czech and other Slavic penal codes as well as the codes of Austrian and German Empires in its Slavic translations. The Polish legal order has not developed any binding instruction on how to interpret grammatical categories, so the question of its correct interpretation constitutes a challenge in the application of law. Verbal aspect, as well as grammatical gender or number, belongs to the most dangerous grammatical categories in the legal use because of the difference between the common sense and its legal meaning.