In general, attitudes to what material is suitable for viewing by younger audiences have changed over the years, and this is reflected by the reclassification of older films being re-released on video. For example, a 1913 film given the former A rating could very probably be rated PG today. An extreme example of this is the rating of the horror film Revenge of the Zombies, with a U certificate upon its video release in the late 1990s, whereas, when it was first examined as a film in 1951, it was given one of the first X ratings.