Buen Día, eh?

Aren’t you glad you’re not in Quebec? Your greetings would be “Bonjour, Hello, Buenos días, eh”.

As an aside, I have asked a few locals about “Buen día” and “Buenos días”. It actually started after I was graciously corrected a couple of times after greeting a person with “Buen día.

The explanation I was given was that “Buenos días” is a greeting of “Good morning” and “Buen día” is a departure comment like “Have a good day.”

Has anyone else had a similar explanation?

I have been told that they are equivalent but the explanation given to you makes more sense. It is indeed a subtle distinction. However, it probably differs from region to region. We need a native speaker.

Their use is interchangeable. It's a matter of custom. Traditionally, formally and possibly most correctly we use "¡buenos días¡" as the standard greeting. But then some people got to thinking, "why plural if it's only one person?" or simply "why plural?" since in other languages the singular is used. So during recent years we hear and use much more frequently "¡buen día!" You'll also hear similarly but much less frequently "¡buena tarde!" and "¡buena noche!" The singular forms are considered popular, localismos, though they seem more common in Mexico and Argentina than other Spanish-speaking countries