Bilo da dođe danas bilo da dođe kasnije, pregled je potreban.

It means whether ... or whether ..., or more loosely whether ... or ... / no matter whether ... or ....

So the pattern:

bilo da X, bilo da Y, ...

introduces two alternative situations, and the main clause stays true in either case.

In this sentence, the idea is:

• bilo da dođe danas = whether he/she comes today
• bilo da dođe kasnije = whether he/she comes later

and in both cases:

• pregled je potreban = the examination/check-up is necessary

Not in the way a beginner might first think.

Historically, bilo does come from biti (to be), but in modern Serbian bilo da is best learned as a fixed conjunction-like expression. In this sentence, it does not literally mean it was.

So don’t try to read:

• bilo = was
• da = that

as separate literal pieces here.

Instead, learn bilo da as a unit meaning something like whether.

Because Serbian often repeats it before each alternative:

• bilo da dođe danas, bilo da dođe kasnije...

This is a very normal pattern and gives a balanced, parallel structure.

In English, we usually say whether ... or ..., with whether only once. Serbian often likes the full repetition more than English does.

You can sometimes shorten it, especially when the subject and verb are the same:

• Bilo da dođe danas ili kasnije, pregled je potreban.

That also works. The repeated version is just fuller and slightly more formal or emphatic.

Because dođe is from the perfective verb doći (to come / to arrive), and here Serbian is talking about a single possible event: the person’s arrival.

• dođe = 3rd person singular present of doći
• dolazi = 3rd person singular present of dolaziti

The difference is mainly aspect:

• doći / dođe = perfective, one completed arrival
• dolaziti / dolazi = imperfective, repeated, ongoing, or habitual coming

In this sentence, the meaning is about a single occasion: whether the person comes today or later. That is why dođe is the natural choice.

If you used dolazi, it would sound more like a habitual or ongoing situation, which does not fit as well here.

Because Serbian often uses the present form in subordinate clauses even when English would think of the future.

After conjunctions such as:

• ako = if
• kad = when
• čim = as soon as
• bilo da = whether

Serbian commonly uses present-tense forms to talk about future situations.

So:

• Ako dođe, javi mi. = If he/she comes, let me know.
• Kad dođe, razgovaraćemo. = When he/she comes, we’ll talk.
• Bilo da dođe danas... = Whether he/she comes today...

That is normal Serbian grammar.

The subject is implied.

Serbian often omits subject pronouns when the verb form already shows the person and number, or when the subject is clear from context.

Here, dođe is 3rd person singular, so it can mean:

• he comes
• she comes
• it comes

depending on context.

If needed for clarity or emphasis, Serbian could include the pronoun:

• Bilo da on dođe danas...
• Bilo da ona dođe danas...

But normally, leaving it out is perfectly natural.

Pregled is in the nominative singular because it is the grammatical subject of the clause:

• pregled je potreban

The adjective potreban agrees with pregled in gender, number, and case:

• pregled = masculine singular
• potreban = masculine singular

So the agreement is:

• masculine: pregled je potreban
• feminine: kontrola je potrebna
• neuter: ispitivanje je potrebno

This is just normal adjective agreement in Serbian.

Both are possible.

Serbian word order is more flexible than English word order, and the difference is usually about emphasis, rhythm, or style.

• Pregled je potreban. = neutral, straightforward
• Potreban je pregled. = slightly more emphasis on the fact that something is necessary

So the sentence could also be:

• Bilo da dođe danas, bilo da dođe kasnije, potreban je pregled.

That would still be correct.

Yes, absolutely.

That shortened version is natural because the subject and verb are the same in both alternatives, so Serbian can avoid repeating them.

Compare:

• Bilo da dođe danas, bilo da dođe kasnije, pregled je potreban.
• Bilo da dođe danas ili kasnije, pregled je potreban.

The full repeated version is more symmetrical and a bit more formal or deliberate. The shorter version is more compact.

Kasnije means later.

In this sentence, it means at a later time than today or not today, but later, depending on context.

It is an adverb, and it does not need a noun after it here. Serbian can simply say:

• danas = today
• kasnije = later

So the contrast is very natural:

• danas vs. kasnije

Because the sentence begins with a subordinate clause, and then the main clause follows.

Structure:

• Bilo da dođe danas bilo da dođe kasnije = subordinate part
• pregled je potreban = main clause

In Serbian, when a dependent clause comes before the main clause, it is normally separated by a comma.

So the comma marks the boundary between:

1. the whether...whether... clause
2. the main statement

That is why the comma appears before pregled je potreban.