Good evening Emanuele and welcome to the Events Calendar Support forum!
Thank you for reaching out to us.
I would love to help you with this topic.
I’m using the PRO version of the plugin in Italian language. The translation is incomplete so I updated the .PO file.
You are right, sometimes the translations found in the plugin folder are not 100% up to date, but the good news is that the ones found on GlotPress are. Here’s the link in case you don’t have it: http://translations.theeventscalendar.com/projects
As for the time/data format, instead of changing the code in the plugin itself, I would recommend going to Events -> Settings -> Display and changing the time related settings.
Let me know if that helps.
Have a great day!
Geoff B.