"Het Wilhelmus", fully known as "Wilhelmus van Nassouwe", is the national anthem of the Netherlands and the former national anthem of the Netherlands Antilles until 1964. Known since at least the 16th century – around the time of the Dutch Revolt – this song contains the oldest melody among all national anthems of the world. Its lyrics also date back to the 1500s, though the lyrics of "Kimigayo"—Japan's national anthem—are much older. Because "Het Wilhelmus" is so old, the origins of the composer(s) and author(s) are uncertain, but the melody has been arranged by Dutch composer Adrianus Valerius in the 1600s. It wasn't officially adopted as national anthem of the Netherlands until the 20th century.