Question: When was the anthem that Philips of Marnix likely wrote recognized as official?
Sentence (from "Philips of Marnix, Lord of Saint-Aldegonde"): Philips of Marnix, Lord of Saint-Aldegonde, Lord of West-Souburg (Dutch: Filips van Marnix, heer van Sint-Aldegonde, heer van West-Souburg, French: Philippe de Marnix, seigneur de Sainte-Aldegonde; Brussels, 7 March/20 July 1540 – Leiden, 15 December 1598) was a Flemish and Dutch writer and statesman, and the probable author of the text of the Dutch national anthem, the "Wilhelmus".
Relevant evidence: Yes