Nadchodzi dzień wymiany ubrań.

Nadchodzi is the 3rd person singular present tense of nadchodzić.

Here it means something like:

• is approaching
• is coming
• is drawing near

So Nadchodzi dzień wymiany ubrań literally means The day of the clothes exchange is approaching.

A useful breakdown is:

• nad- = a prefix here giving the idea of something coming near
• chodzić = to go / walk (in a frequentative sense)
• nadchodzić = to approach, to come nearer in time or space

In this sentence it is used about an upcoming day or event, which is very natural in Polish.

Yes, you can also say Dzień wymiany ubrań nadchodzi.

Polish word order is much more flexible than English word order because cases show grammatical roles. In this sentence:

• Nadchodzi dzień wymiany ubrań sounds a bit more like The clothes-swap day is coming / Here comes the clothes-swap day
• Dzień wymiany ubrań nadchodzi puts more focus on the day itself

Both are grammatical.

Very roughly:

• verb first can sound more dynamic or literary
• subject first can sound more neutral or straightforward

So the original sentence is completely natural, but not the only possible order.

Dzień is in the nominative singular.

It is the subject because it is the thing that is approaching. The verb nadchodzi is 3rd person singular, and dzień matches that.

Even though the subject comes after the verb, Polish allows that. English relies heavily on word order, but Polish does not need to.

So:

• nadchodzi = is approaching
• dzień = day → the thing doing that action

Because after dzień you often get a noun phrase meaning day of something, and that something goes into the genitive.

So:

• wymiana = exchange, swap (dictionary form, nominative)
• wymiany = of exchange / of swapping (genitive singular)

This is a very common pattern in Polish:

• dzień pracy = day of work
• dzień ślubu = wedding day / literally day of the wedding
• dzień wymiany ubrań = day of clothes exchange

You can think of it as:

• dzień
  • czego? (of what?) → wymiany

Because wymiana itself also usually takes the genitive when you say what is being exchanged.

So the structure is:

• dzień
  • wymiany
• wymiana
  • ubrań

That gives a kind of chain:

• dzień (day)
• wymiany (of exchange)
• ubrań (of clothes)

So literally it is:

day [of exchange [of clothes]]

This kind of stacked genitive structure is very common in Polish.

The base form is ubranie.

Here is the pattern:

• ubranie = a garment / an item of clothing
• ubrania = clothes / clothes items (plural nominative or accusative)
• ubrań = of clothes (genitive plural)

In this sentence, the genitive plural is required because it depends on wymiany.

So:

• wymiana ubrań = exchange of clothes / clothes swap

Because ubrania often refers to clothes as separate items, which fits the idea of a swap very well.

Compare:

• ubrania = clothes, garments
• odzież = clothing, often a bit more formal or collective

So:

• wymiana ubrań = very natural for a clothes swap
• wymiana odzieży = also possible, but often sounds more formal

A native speaker would likely find ubrania very normal in this context.

Yes, it is natural, especially in an announcement, event description, poster, or social-media post.

It has a slightly promotional or event-like tone, something like:

• The clothes swap day is coming
• The day of the clothes exchange is approaching

In everyday speech, people might also say:

• Zbliża się dzień wymiany ubrań
• Już niedługo dzień wymiany ubrań
• Niedługo odbędzie się wymiana ubrań

So the original sentence is correct and natural, but there are several equally natural alternatives depending on style.

Both can mean is approaching, but they feel slightly different.

• nadchodzi = is coming, is drawing near
• zbliża się = is getting closer, is approaching

In many contexts they are interchangeable.

However:

• nadchodzi can sound a bit more vivid or literary
• zbliża się often sounds a bit more neutral and common in everyday use

So:

• Nadchodzi dzień wymiany ubrań = a bit more dramatic or event-like
• Zbliża się dzień wymiany ubrań = very standard and neutral

Because Polish has no articles like a or the.

So dzień can mean:

• a day
• the day

The exact meaning depends on context.

In this sentence, English usually needs the:

• The clothes swap day is approaching
• or more naturally, The day of the clothes swap is approaching

But Polish does not need any article to express that.

Yes. The phrase dzień wymiany ubrań can be understood either as:

• a specific event name, like Clothes Swap Day
• or simply a day for exchanging clothes

Polish often leaves that slightly open unless the wider context makes it clear.

For example:

• in an event announcement, it may sound like a named event
• in ordinary description, it may just mean the day when clothes will be exchanged

So the phrase is grammatically the same, and context decides how specific it feels.