Hi Carlos,
You only use an ordinal number for the first of the month in French 1 er-
C'est le 1 er avril != it's the 1st of April !
You wouldn't use 2e, 3e etc, as you suggest for the rest of the days with dates.
It is nothing to do with being the purest, it is simply wrong.
Maybe non-French people do this. I'd be very surprised to learn that something as basic as this has changed in France ...
Bonne Continuation!
