Learn Hardcore Croatian: Danas je nedjelja.

danas = adverb “today” (not the subject)
je = 3rd person singular present of biti “to be” (an unstressed clitic verb)
nedjelja = noun “Sunday” (feminine, nominative singular) — this is the subject

Why is it je and not some other form of “to be”?

Because the subject (nedjelja) is 3rd person singular. Present tense of biti:

ja sam
ti si
on/ona/ono je
mi smo
vi ste
oni/one/ona su

Where does je go in the sentence?

Je is a clitic and normally sits in “second position” in the clause, after the first stressed word or phrase:

Danas je nedjelja.
Nedjelja je danas. With longer starts, it still follows the first phrase: Sutra ujutro je ispit.

Can I leave out je?

In standard, neutral sentences you keep it. You might see it omitted in headlines or notes (e.g., Danas nedjelja.), but in regular speech and writing you should say Danas je nedjelja.

Why isn’t “Sunday” capitalized?

In Croatian, days of the week (and months) are not capitalized unless they begin a sentence or are part of a proper name. So nedjelja is lowercase here.

Why is there no article (“a/the”)?

Croatian has no articles. Danas je nedjelja. covers English “It’s Sunday/It is a Sunday” depending on context.

Why is it nedjelja and not nedjelju?

With biti (“to be”), both sides are in the nominative: nedjelja (nom.). You use nedjelju (acc.) after certain prepositions, for example:

“on Sunday” = u nedjelju
“every Sunday” (habitually) = nedjeljom (an adverbial form)

How do I ask this as a yes/no question?

Standard: Je li danas nedjelja?
Colloquial contraction: Je l’ danas nedjelja? In Croatia, je li is preferred in standard use; da li is more Serbian/regional.

How do I ask “What day is it today?”

Koji je danas dan? Answer: Danas je nedjelja.

How do I negate it?

Danas nije nedjelja.
You can add a correction: Danas nije nedjelja, nego subota.

How do I pronounce it?

j is like English “y”: je = “ye”
lj is a palatal L, like the “lli” in “million”: lj ≈ “ly” Approximate: DAH-nahs yeh NEH-dye-lya

Can I start with “Nedjelja” instead?

Yes: Nedjelja je danas. That puts emphasis on “Sunday” (It’s Sunday today), while Danas je nedjelja is the neutral, most common order.

What’s the difference between nedjelja and nedelja?

Nedjelja is standard Croatian. Nedelja is the Serbian form. You may also hear dialectal Croatian nedilja.

How do I say “on Sunday” and “every Sunday”?

“on Sunday” (a specific Sunday): u nedjelju
“every Sunday” (habitually): nedjeljom
Examples: Idem u crkvu u nedjelju. / Radim nedjeljom.

How would I say “Yesterday was Sunday” and “Tomorrow is Monday”?

Jučer je bila nedjelja. (past feminine participle bila agrees with feminine nedjelja)
Sutra je ponedjeljak.

Can I use jest instead of je?

Jest is the full, emphatic form, used for stress or in the fixed expression to jest (“that is to say”). Danas jest nedjelja sounds emphatic/marked. In everyday speech, use je.