Here http://wildlatina.co/product/cindy/ you can see the comment date format is 7 Octubre, 2017 and how to make it like this 7 de Octubre, 2017, for all the comments add “de” in between the month and day. I believe it would be a php snippet? I have a code snippet plugin installed.
Usually the time and date format are set in “Settings > General”. However, I’m not sure how you could add a word like “de” to it – I’ve never seen a function or filter like that. Have you checked with WordPress.org support? They may have seen something similar before.