sudanglo:The customary scope of antaŭtagmeze/posttagmeze or antaŭtagmezo/posttagmezo (ie the full forms) may indeed be different to the usage of atm and ptm (preceded by times).

Chapeau!

I totally agree with you. While I use "8 AM", "2 PM" and "6 PM" with the abbreviated forms, I would say "8 in the morning", "2 in the afternoon" and "6 in the evening".

Maybe "AM" and "PM" are more "mathematical" and more abstract concepts than their full forms.

Kirilo81:This is really an intriguing question (and a nice idea to solve the contradiction). I'll note it and perhaps (I'm applying for a position where I could actually do qualitative research with Esperanto speakers) I'll actually be able to query congress participants about it.

That's an interesting idea. In the meantime, why not make an informal poll in the "Vidpunktoj" section? You can also ask about what language everyone speaks to see how that relates to everyone's understanding of atm/ptm.