Calendar language

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How to change calendar language from English to Croatian, so that doesn?t

says ?Ovaj proizvod je upisan u na?u trgovinu dana Friday 01 September, 2006?.

It should be ?Ovaj proizvod je upisan u na?u trgovinu dana Petak 01 Rujna, 2006?

it mean: ?This product was added to our catalog on Friday 01 September, 2006."

I found on forum that I have to change events_calendar.php under includes/languages/croatian/

But I have no that file.