Learn Croatian: Poznati pisac je umro tisuću osamsto osamdeset prve godine. - The famous writer died in eighteen eighty-one.

In English you say "in eighteen eighty-one", but in Croatian, years are expressed using ordinal numbers. You are literally saying "in the thousand eight hundred eighty-first year". To express "when" an event happened, this ordinal number and the word for year (godina) must be put into the genitive case, making it prve godine.

If the year is in the genitive case, why don't tisuću, osamsto, and osamdeset change their endings too?

When saying long numbers or years in Croatian, only the very last word acts as an adjective and changes its case. The earlier parts of the number stay completely unchanged. That is why only prvi changes to prve to match the feminine genitive noun godine.

Why is 800 written as one word (osamsto) instead of two (osam stotina)?

Both forms are correct, but adding the suffix -sto directly to the single-digit number is a much faster and more common way to express hundreds in Croatian. This shorter form is especially popular when reading out long numbers like years.

Why does the sentence use je umro instead of just umro for "died"?