Datum sastanka je već upisan u kalendar.

Because sastanka is in the genitive singular.

In datum sastanka, the second noun tells us what kind of date it is: the meeting’s date or the date of the meeting. Croatian often expresses this relationship with:

• noun + genitive noun

So:

• datum = date
• sastanak = meeting
• datum sastanka = the date of the meeting

This is very common in Croatian:

• ime grada = the name of the city
• vrata kuće = the door of the house
• početak filma = the beginning of the film

Because datum is the subject of the sentence.

The core structure is:

• Datum sastanka = subject
• je upisan = predicate

Croatian marks the subject with the nominative case, so datum stays in its basic dictionary form here.

Upisan is a past passive participle from the verb upisati.

Here it means something like:

• written in
• entered
• recorded

In this sentence, je upisan forms a passive/resultative idea:

• je upisan = has been entered / is entered / is already written in

It agrees with datum, which is:

• masculine
• singular

So we get upisan.

Compare:

• Datum je upisan. → masculine singular
• Adresa je upisana. → feminine singular
• Pisma su upisana. → neuter plural / plural form would change accordingly depending on the noun

Because the sentence focuses on the state/result, not on who did the action.

• upisuje = is writing/entering or writes/enters
• upisao = wrote/entered but usually refers to a male person who performed the action
• je upisan = has been entered / is entered

So:

• Netko je upisao datum u kalendar. = Someone entered the date in the calendar.
• Datum je upisan u kalendar. = The date has been entered in the calendar.

The second version is natural when the doer is unknown, unimportant, or obvious.

Već means already.

In this sentence it emphasizes that the action has happened before now, perhaps sooner than expected or before someone asked about it.

• Datum sastanka je već upisan u kalendar.

Croatian word order is flexible, so već can move around, but not every position sounds equally natural. In this sentence, placing it before upisan is very natural.

Possible variants:

• Datum sastanka je već upisan u kalendar.
• Datum sastanka već je upisan u kalendar.

Both are fine, though the first often sounds more neutral in everyday speech.

Because after u, Croatian can use either:

• accusative for movement into
• locative for location in

Here, upisati u kalendar is understood as entering something into the calendar, so u takes the accusative:

• kalendar → accusative singular: kalendar

Compare:

• upisati u kalendar = to enter into the calendar
• u kalendaru piše... = it says in the calendar

In the second example, we are talking about location, so we use locative:

• u kalendaru

Yes, absolutely. This is one of those places where Croatian and English organize the idea differently.

English says:

• in the calendar

Croatian often uses u + accusative with verbs of putting, entering, writing, inserting, etc., because the action is seen as going into something:

• staviti u torbu = put into the bag
• upisati u bilježnicu = write into the notebook
• unijeti u sustav = enter into the system

So even if the best English translation uses in, Croatian may still use the structure that corresponds more closely to into.

Usually yes, when you mean a calendar date.

For example:

• Koji je datum danas? = What’s the date today?
• Datum rođenja = date of birth
• Datum sastanka = meeting date

Just note that datum is a somewhat international-style word, and in some contexts Croatian speakers may also use other expressions depending on meaning. But for standard calendar-date usage, datum is completely normal.

Usually datum sastanka is the more natural choice for the date of the meeting.

• datum sastanka = the meeting’s date / the date of the meeting

datum za sastanak could sound more like:

• a date intended for the meeting
• a proposed or assigned date for a meeting

So the nuance is different. If you are simply naming the meeting date as a fact, datum sastanka is the standard phrasing.

It can mean both, depending on context.

Upisati is broader than just physically writing by hand. It can be used for:

• writing something into a notebook
• entering information into a calendar
• typing something into a computer system
• registering information officially

So in this sentence, upisan u kalendar could mean:

• written in a paper calendar
• entered into a digital calendar

If the speaker wanted to be more specific about digital entry, they might choose a verb like unesen in some contexts, but upisan is still very natural.

The basic verb here is upisati, which is perfective.

That means it refers to a completed action: the date got entered.

Its imperfective partner is usually upisivati:

• upisivati = to be entering, to enter repeatedly, to enter over time
• upisati = to enter, to write down completely

In this sentence, the perfective sense fits well because the result is complete:

• the date is already entered

Yes. Croatian word order is fairly flexible, though some versions sound more neutral than others.

Standard neutral order:

• Datum sastanka je već upisan u kalendar.

Other possible orders:

• Datum sastanka već je upisan u kalendar.
• U kalendar je datum sastanka već upisan.
• Već je datum sastanka upisan u kalendar.

Changing the order changes emphasis:

• putting već earlier emphasizes already
• putting u kalendar earlier emphasizes where
• keeping datum sastanka first is the most straightforward, neutral option

Yes, but the nuance changes a little.

• upisan = entered/written in, often into a list, record, calendar, or register
• unesen = entered/input, often sounds a bit more technical or digital
• zapisan = written down
• zabilježen = noted/recorded

So:

• Datum sastanka je već upisan u kalendar.
  Very natural for a calendar.

• Datum sastanka je već unesen u kalendar.
  Also very natural, especially for a digital calendar.

• Datum sastanka je već zapisan u kalendar.
  Understandable, slightly more focused on writing it down.

• Datum sastanka je već zabilježen u kalendaru.
  Also possible, though this may sound a bit more formal or descriptive.

For a basic learner sentence about calendars, upisan is an excellent choice.