mesec dana - one month godinu dana - one year these expressions are usually used to express when something will happen, e. g. za mesec dana / za godinu dana - in a month / in a year i hope this helped

Jedan dan. (singular) Dva dana, tri dana, četiri dana, pet dana, mesec dana, godinu dana.... (plural) Counting in Croatian is quite complicated, and I usually teach this only to advanced students. If you are a beginner, it might be difficult to swallow. Try to memorize it now as a phrase, and when you get more into the language and learn how it works (and generally, how Slavic languages work, it might become clearer). Sorry, it might not be the answer you expected to, but I am telling you from the experience. Like, when I was learning Japanese, I couldn't understand why adjectives have a past tense form. But it just dawned on me one day.