what does 17.9.1991 mean? Can I suggest people stop coming up with their novel date formatting schemes and use a standard that universally makes sense? ISO 8601 is worth looking at:
The ISO standard is great for data exchange, but it's unlikely to change how dates are normally spoken and casually written.
My native format is mdy but I dislike it almost as much as dmy.
Danish: klokken 14
German: 14 Uhr
That does mean native speakers of languages like this might say "14 o'clock" when speaking English.
I very occasionally use this if I need to be certain to be understood by someone who rarely speaks English, "we'll arrive at 19 o'clock". (A friend's parents in rural rest-of-Europe, for example.)