Change date format

Hi.

I use template paperbox (which is currently not supported – author is not responding) and I want to customize date format in posts. It seems like the theme uses custom date format and translations, because I can’t change date format using default settings in WP admin. And I want to translate the date (names of months) to my local language.

But I am not able to find the file where is the translation. Is it somehow possible to find out where are stored names of months in my template? I tried to find it using
grep -H -r "July" /var/www/html/selfici.com/wp-content/themes/paperbox/ (I have my website on linux VPS) but I was not successful. I also tried to find it using Adminer directly in my database but I was not sucessful as well. So it looks like it is defined nowhere, but it has to be somewhere ??

So is there any way how to find names of months and translate it directly to my local language?

My website is https://www.selfici.com/cs/