Dziewiątego stycznia mam ważne spotkanie w biurze.

Because Polish expresses dates with special case forms.

In Dziewiątego stycznia:

• dziewiątego = ninth in the genitive
• stycznia = January in the genitive

Polish commonly says dates in a form equivalent to on the ninth of January.

So:

• dziewiąty styczeń is not how dates are normally said
• the natural date expression is dziewiątego stycznia

You will often see the pattern:

• pierwszego maja = on the first of May
• trzeciego lipca = on the third of July
• dziewiątego stycznia = on the ninth of January

Stycznia is the genitive singular of styczeń.

Dictionary form:

• styczeń = January

In date expressions, month names usually appear in the genitive:

• stycznia
• lutego
• marca
• kwietnia

So in this sentence, stycznia is genitive because that is the normal case used for months in dates.

Because the day number agrees with the month expression in the date structure.

In Polish, when you say a date like the ninth of January, the ordinal number is also put in the genitive:

• pierwszego maja
• drugiego czerwca
• dziewiątego stycznia

So dziewiątego is the genitive form of dziewiąty.

This is one of those patterns that is best learned as a whole date formula.

Polish often does not need a separate word equivalent to English on before dates.

So English:

• On the ninth of January I have an important meeting

Polish:

• Dziewiątego stycznia mam ważne spotkanie

The date phrase by itself already works adverbially, so no extra preposition is required.

You may sometimes hear other date-related structures in Polish, but here Dziewiątego stycznia alone is perfectly normal.

Yes, literally it means I have an important meeting, and that is also a very natural way to say this in Polish.

Polish often uses mieć for planned events, obligations, appointments, and meetings:

• Mam spotkanie = I have a meeting
• Mam egzamin = I have an exam
• Mam wizytę u lekarza = I have a doctor’s appointment

So even if English might sometimes say There is or I’m meeting someone, Polish very commonly uses mam.

Because the adjective must agree with the noun in gender, number, and case.

Here:

• spotkanie is neuter singular
• it is the direct object of mam
• for this noun, the accusative singular looks the same as the nominative singular

So the adjective must match:

• ważne spotkanie

Compare:

• ważny problem — masculine
• ważna sprawa — feminine
• ważne spotkanie — neuter

It is in the accusative singular, because it is the direct object of mam.

You have something, so that thing is the object:

• mam co? → spotkanie

However, with many neuter singular nouns in Polish, the accusative form is identical to the nominative form. That is why spotkanie looks unchanged.

So grammatically it is accusative, even though its form is the same as nominative.

Because w can take different cases depending on the meaning.

Here it means in or at a location, so it takes the locative:

• w biurze = in the office

If there were movement into a place, Polish would typically use a different structure, often with the accusative:

• idę w stronę biura or idę do biura = I’m going to the office

So:

• w biurze = location
• do biura = movement toward the office

That is why biuro changes to biurze here.

Biurze is the locative singular of biuro.

Dictionary form:

• biuro = office

After w meaning in/at, the noun usually goes into the locative:

• w domu = in the house
• w szkole = at school
• w biurze = in the office

So biurze is used because the sentence describes where the meeting takes place.

Because Polish usually drops subject pronouns when the verb already makes the subject clear.

Here:

• mam already means I have

So ja is unnecessary in a neutral sentence.

You could say:

• Ja mam ważne spotkanie w biurze

but that would usually add emphasis, contrast, or emotion, something like:

• I have an important meeting
• As for me, I have an important meeting

In normal speech, just mam is enough.

Yes. Polish word order is more flexible than English, although not completely free.

The sentence:

• Dziewiątego stycznia mam ważne spotkanie w biurze

is natural and neutral.

Other possible orders include:

• Mam ważne spotkanie w biurze dziewiątego stycznia
• W biurze mam ważne spotkanie dziewiątego stycznia
• Ważne spotkanie mam dziewiątego stycznia w biurze

But changing the order changes the emphasis.

For example:

• starting with Dziewiątego stycznia highlights the date
• starting with W biurze highlights the location
• starting with Mam sounds more like a plain statement

So the original version is a good, natural choice.

Usually no. In standard Polish, names of months are written with a lowercase letter.

So:

• stycznia is correct
• Stycznia would normally be wrong in the middle of a sentence

This is different from English, where January is capitalized.

Yes. That is very common in writing.

You can write:

• 9 stycznia mam ważne spotkanie w biurze.

When speaking, however, you would normally read that as:

• Dziewiątego stycznia mam ważne spotkanie w biurze.

So:

• 9 stycznia is common in writing
• dziewiątego stycznia is the normal spoken form

It most often means meeting, but depending on context it can also correspond to appointment.

For example:

• mam spotkanie z klientem = I have a meeting with a client
• mam spotkanie w biurze = I have a meeting in the office

If you want to stress a more formal scheduled appointment, Polish may also use words like wizyta in some contexts, especially for doctors, salons, and similar situations.

But in this sentence, spotkanie is exactly the natural word for meeting.