I think the text that doesn’t work as expected is js.dates.long_with_year. While the English version is MMM D, YYYY h:mm a, the Croatian version is D MMM, YYY h:mm, so there is one Y missing. You should be able to customize that on your site like any other text.
If that fixes the problem, it would be great if you could also improve this text for all forums where users use the Discourse interface in Croatian by improving the translation on Crowdin. (If you struggle with the interface of Crowdin, I’m happy to help. Alternatively, I can suggest the change if you tell me what it should be. You can learn more about the date formats of moment.js here)
Thank you for improving the translation of Discourse!