Learn Hardcore Czech: Včera bylo v knihovně zavřeno kvůli prázdninám. - Yesterday the library was closed because of the school holidays.

Czech often uses an impersonal construction with the neuter singular to talk about states or situations without naming a clear subject. Literally, the structure is like:

Bylo zavřeno. – It was closed. (but “it” is not a real thing; it’s just the situation)

So:

Včera bylo v knihovně zavřeno
literally: Yesterday was in the library closed
meaning: Yesterday, the library was closed.

The logical subject is knihovna (the library), but grammatically it is not expressed as the subject: the sentence is built impersonally around bylo zavřeno.

What exactly is zavřeno? Why does it end in -o?

Zavřeno is a short neuter form of a passive/resultative participle from the verb zavřít (to close).

In this impersonal structure:

bylo zavřeno – it was closed

Here:

bylo – past tense of být, neuter
zavřeno – neuter, agreeing with the impersonal neuter construction

Compare to an adjectival form that directly describes a feminine noun:

Knihovna byla zavřená. – The library was closed.
(knihovna feminine, so zavřená feminine)

So:

bylo zavřeno – impersonal, more about the state of things / situation
byla zavřená (knihovna) – personal, with knihovna as a clear subject

What is the difference between Včera bylo v knihovně zavřeno and Včera byla knihovna zavřená?

Both basically mean “Yesterday, the library was closed.” but they feel slightly different:

Včera bylo v knihovně zavřeno.
- Impersonal construction.
- Focuses on the fact that the place was closed, the situation.
- Very common in signs, announcements, or neutral narration.
Včera byla knihovna zavřená.
- Personal construction with knihovna as the subject.
- Feels a bit more like you are talking about the library as an entity.
- The adjectival form zavřená agrees with knihovna (feminine).

Both are correct and natural. In everyday speech you will hear both; bylo zavřeno is just a very typical pattern for “X was closed” about places, shops, etc.

Why is it kvůli prázdninám and not kvůli prázdniny?

The preposition kvůli (because of, due to) requires the dative case.

Base form (nominative plural): prázdniny – holidays, school break
Dative plural: prázdninám

So:

kvůli prázdninám = because of the holidays
(literally: due to holidays-DATIVE)

Using kvůli prázdniny would be incorrect, because prázdniny is nominative/accusative plural, not dative.

Why is it prázdniny (plural) when in English we might say “holiday” (singular)?

In Czech, prázdniny is almost always plural-only (pluralia tantum). It refers to:

school holidays / vacation periods – summer holidays, winter break, etc.

Examples:

letní prázdniny – summer holidays
jarní prázdniny – spring break

If you want to refer to a single holiday / public holiday, you typically use:

svátek – public holiday, feast day
- Včera byl státní svátek. – Yesterday was a public holiday.

So:

kvůli prázdninám – because of the school holidays / vacation period(s)
kvůli svátku – because of a (single) holiday / public holiday

What case is v knihovně, and how is it formed from knihovna?

V knihovně is:

Preposition: v (in)
Case: locative singular
Noun: knihovna (library), feminine

Declension:

Nominative: knihovna – (the) library
Locative: (v) knihovně – in the library

With location after v, Czech usually uses the locative case:

v knihovně – in the library
v Praze – in Prague
v obchodě – in the shop

Can I change the word order, for example: Včera v knihovně bylo zavřeno kvůli prázdninám?

Yes, Czech word order is flexible, and that version is correct:

Včera v knihovně bylo zavřeno kvůli prázdninám.

Common natural options include:

Včera bylo v knihovně zavřeno kvůli prázdninám. (original)
Včera v knihovně bylo zavřeno kvůli prázdninám.
Včera bylo kvůli prázdninám v knihovně zavřeno.

The main neutral pattern keeps:

Time: Včera
Verb + participle: bylo zavřeno
Place and reason: v knihovně kvůli prázdninám

But as long as you don’t break fixed combinations (like kvůli + dative), different orders are acceptable and often just change the focus (what you want to emphasize).

How would I say “Tomorrow the library will be closed because of the holidays” in a similar style?

You can keep the same impersonal pattern and change the time and tense:

Zítra bude v knihovně zavřeno kvůli prázdninám.
– Tomorrow, the library will be closed because of the holidays.

Changes:

Včera bylo → Zítra bude
(past bylo → future bude)
The rest stays the same.

A personal variant is also possible:

Zítra bude knihovna zavřená kvůli prázdninám.

What’s the difference between kvůli prázdninám and během prázdnin?

Both mention prázdniny, but they express different relations:

kvůli prázdninám – because of the holidays
- Reason / cause
- The holidays are the cause of the closure.
- Včera bylo v knihovně zavřeno kvůli prázdninám.
  – Closed yesterday because of the holidays.
během prázdnin – during the holidays
- Time period
- Says when something happens, not necessarily why.
- Během prázdnin je knihovna zavřená.
  – The library is closed during the holidays.

So:

Use kvůli when you want to state the reason.
Use během when you want to state the time frame.

How do I turn this sentence into a question or a negative sentence?

Yes–no question

Just use question intonation (and optionally change word order slightly):

Bylo včera v knihovně zavřeno kvůli prázdninám?
– Was the library closed yesterday because of the holidays?

Negative statement

Negate bylo → nebylo:

Včera nebylo v knihovně zavřeno kvůli prázdninám.
– Yesterday, the library was not closed because of the holidays.

Negative question

Neb ylo včera v knihovně zavřeno kvůli prázdninám?
– Wasn’t the library closed yesterday because of the holidays?