Ok, the Italian translation is supposed to be complete although "complete" does not guarantee you any quality or that every word would be translated. Anyway, the names of months and days are localizable and should have been translated. If there is a problem with the translation though, like the person who did it entered Monday for Monday instead of what it should be in the corresponding language, you can change this buy correcting the translation from the site ( the one that you are currently using ). Use the directions given at http://rainlendar.net/cms/index.php?option=com_rny_translate
and you can even get a free license for the Pro version. (this would be up to Rainy though)
If you don't want to do this or can't figure out how you could try contacting the person that did the localization in the first place and send him a suggestion on what a certain entry should say.