Thanks for your answer !
Currently, there isn’t any language plugin installed on my website : the only language used is french. All my rooms informations are wrote in this language. If I understand Vibooking’s backend correctly, I am able to set translations for other languages, in my example english, which will be visible once I install a language plugin and view my website as an english user.
So my problem is that even if french is currently set as the main language of my website, the datepickers appear in english. I simply want to know if I am missing something.