È stata una brutta serata.

Both are possible, but they are not exactly the same.

• È stata is the passato prossimo of essere.
• Era is the imperfetto of essere.

In this sentence, È stata una brutta serata presents the evening as a completed event: the evening happened, and now we are looking back on it as a whole.

Era una brutta serata sounds more like description or background. It can mean it was a bad evening, but it often feels less like a finished event and more like setting the scene.

So, if you are commenting afterward on how the evening went, È stata una brutta serata is very natural.

È stata is the third-person singular passato prossimo of essere.

It is made of:

• è = is / has as the auxiliary form of essere
• stata = past participle of essere

So the structure is:

• essere in the present tense + past participle

For essere, the passato prossimo is:

• sono stato/stata
• sei stato/stata
• è stato/stata
• siamo stati/state
• siete stati/state
• sono stati/state

In this sentence, stata agrees with serata, which is feminine singular.

Because the thing being referred to is una serata, and serata is a feminine singular noun.

With essere, the past participle usually agrees in gender and number with the subject or the thing being referred to. So:

• masculine singular: stato
• feminine singular: stata
• masculine plural: stati
• feminine plural: state

Since serata is feminine singular, we say:

• È stata una brutta serata

not

• È stato una brutta serata

Una is the indefinite article, meaning a/an.

So:

• una serata = an evening / a night
• una brutta serata = a bad evening

Italian normally uses the article here just as English does. Since serata is feminine singular, the correct article is una.

Compare:

• un giorno = a day
• una notte = a night
• una serata = an evening

This is a very common question.

• sera usually means evening in a general time-of-day sense.
• serata often refers to the evening as an event or experience, like the evening/night out.

So:

• stasera = this evening / tonight
• Che fai stasera? = What are you doing this evening?

But:

• Abbiamo passato una bella serata = We had a lovely evening
• È stata una brutta serata = It was a bad evening

In your sentence, serata is used because we are talking about the whole experience of that evening, not just the time period.

In Italian, many common descriptive adjectives can come before the noun, especially in everyday speech.

So una brutta serata is the most natural order here.

If you say:

• una brutta serata

it sounds normal and idiomatic.

You could also hear:

• una serata brutta

but that is less natural in this context and may sound more marked, contrastive, or stylistically unusual.

In general, short, common, evaluative adjectives like bello, brutto, buono, grande, piccolo often appear before the noun.

Yes, it is grammatically possible, but it is not the most natural choice here.

The usual phrasing is:

• È stata una brutta serata

Putting brutta after the noun can sound:

• more emphatic
• more contrastive
• less idiomatic in ordinary speech

A native speaker would normally prefer una brutta serata unless there is a special reason to place the adjective after the noun.

Because that is simply how the adjective brutto is spelled.

Its forms are:

• brutto = masculine singular
• brutta = feminine singular
• brutti = masculine plural
• brutte = feminine plural

The double consonant matters in Italian pronunciation. A double tt is pronounced longer and more strongly than a single t.

So brutta is not pronounced like a simple English-style bruta. The double consonant is part of correct Italian spelling and pronunciation.

The accent is important because è and e are different words.

• è = is
• e = and

So:

• È stata una brutta serata = It was a bad evening
• e stata would be incorrect

In careful writing, even uppercase È should keep the accent.

Literally, yes, it is built like has been, but in Italian it often translates as simple English was.

So:

• È stata una brutta serata

is most naturally:

• It was a bad evening

not usually:

• It has been a bad evening

English and Italian do not always match tense-for-tense. Italian passato prossimo often corresponds to English simple past.

Sometimes, but brutta serata is much more natural here.

• brutto/brutta often means bad, awful, or unpleasant in a broad everyday sense
• cattivo/cattiva often suggests bad in the sense of mean, harmful, morally bad, or sometimes poor quality

So for an unpleasant evening or a night that went badly, Italians would usually say:

• una brutta serata

rather than:

• una cattiva serata

Yes. Italian often leaves out the subject pronoun when it is understood from the verb.

So È stata una brutta serata literally has no written subject pronoun, but in English we supply it:

• It was a bad evening

Italian does this all the time:

• È tardi = It is late
• Piove = It is raining
• È stata una brutta serata = It was a bad evening

A few natural options are:

• È stata una serata davvero brutta = It was a really bad evening
• È stata una brutta, brutta serata = very emphatic
• È stata una pessima serata = It was a terrible evening
• È stata una serata orribile = It was a horrible evening

All of these are possible, but È stata una brutta serata is already very natural and common.

You would change both the noun and the agreeing words:

• Sono state brutte serate

Breakdown:

• sono state = they were
• brutte = feminine plural of brutta
• serate = plural of serata

So the agreement changes from singular to plural:

• È stata una brutta serata
• Sono state brutte serate