Originally Posted by
SeamusSA
First, realize that "Bastille Day" is an English term not used in France, where 14 July is known as <<fête nationale>>
You are right that Bastille day is not an expression that would be recognised in French. However, "fête nationale" is not that common either to refer to the 14th of July. "Fête nationale" might be what they write down on calendars and the like but I can't say that it would be much used in ordinary speech. "Tu fais quoi pour le 14 juillet?" would sound natural whereas many native speakers would wonder what you are talking about if you said "tu fais quoi pour la fête nationale?"