Nope thats Dec 6th ........St Nicholas day
In Belgium (Flanders) and Netherlands a few preliminary (or indeed the main) presents are given out by Sinter Klaas and his assistants Zwarte Pieten (Black Petes) and it's a great excuse for a drink. It doesn't affect air travel these days. As far as I can read the legend, he used to ride a white horse in the sky, which might have led to some NOTAMs, but now he arrives by steamboat.
As for FR it would have affected Eindhoven, but I'm not sure about Charleroi -the legend was in ancient Flanders, which did include Lille (Rijsel) so it's not just a linguistic thing.
No doubt our Low Country friends can enlighten us further.
Happy New Year