Learn Hardcore Portuguese (Portugal): No passado, eu ficava acordado até tarde sem razão. - In the past, I stayed awake until late for no reason.

Eu fiquei acordado até tarde – “I stayed up late (once / on a specific occasion).”
Eu tenho ficado acordado até tarde – “I have been staying up late” (recently, up to now).

In the original sentence, we’re talking about a general habit in the past, so the imperfect ficava is the natural choice.

What exactly does ficava acordado mean? Why use ficar with acordado?

Literally, ficava acordado means “stayed awake”.

In Portuguese, ficar + adjective / past participle often means:

to remain in a state
to end up in a state
or (in the imperfect) to habitually be/remain in that state

Here:

ficar = to stay / remain
acordado = awake (adjective, not the verb “to wake up”)

So:

Eu ficava acordado → “I used to stay awake” / “I used to stay up.”

It’s a very standard way to say “stay up” or “remain awake.”

Could I say eu estava acordado até tarde instead of eu ficava acordado até tarde? What’s the difference?

You can say eu estava acordado até tarde, but there is a nuance:

Eu ficava acordado até tarde
– Emphasises the habit of staying up, the idea of “I used to stay up late” (ongoing habit in the past).
Eu estava acordado até tarde
– Describes your state (“I was awake until late”), a bit more static. Context can make it habitual, but it doesn’t highlight the “staying up” action as strongly.

For “I used to stay up late,” ficava acordado is more idiomatic and natural.
For describing your condition in a particular past situation (“At that time I was awake until late”), estava acordado could fit better.

Do I really need to say eu? Could I just say No passado, ficava acordado até tarde sem razão?

You can absolutely drop eu:

No passado, ficava acordado até tarde sem razão.

Portuguese is a pro-drop language: the verb ending (ficava) already tells you the subject is “eu”.

Using eu:

can add emphasis (e.g., I used to stay up late, as opposed to others)
may feel slightly more explicit or contrastive, depending on context.

Both versions are grammatically correct and natural.
Without special emphasis, many native speakers would omit eu here.

Is No passado the most natural way to say “in the past”? Are there alternatives?

No passado is correct and understandable, but in everyday speech many Portuguese speakers prefer other options, depending on the nuance:

Antigamente, eu ficava acordado… – “In the old days / Back then, I used to stay up…”
Antes, eu ficava acordado… – “Before, I used to stay up…”
No passado, eu ficava acordado… – more neutral, sometimes a bit more formal or written.

All are correct. For casual spoken European Portuguese, Antigamente or Antes often sound more natural than No passado.

Why is it até tarde and not até a tarde or até à tarde?

There is an important distinction:

até tarde
– means “until late” (late at night / late in general, an adverb).
– tarde here is used adverbially, with no article.
até à tarde (with crase in Portugal: à)
– means “until the afternoon” (time period, like “until the afternoon time”).
– tarde is a noun with a definite article: a tarde → à tarde.

So:

Eu ficava acordado até tarde – I used to stay up late (at night).
Eu trabalhava até à tarde – I worked until the afternoon.

In your sentence, we want the idea “late at night,” so até tarde (no article) is correct.

What does sem razão mean here? Why not sem uma razão or sem razão nenhuma?

Sem razão means “for no reason / without any reason” in a general, neutral way.

Alternatives and nuances:

sem uma razão
– “without a reason” (more literal; used less in this kind of sentence).
sem razão nenhuma
– “without any reason at all,” a bit more emphatic.
sem motivo
– “without (a) motive / reason,” very common and natural too.

In your sentence:

sem razão = “for no particular reason,” which fits perfectly.
You could replace it with sem motivo with almost no change in meaning:
- …até tarde sem motivo.

Can I change the word order to No passado, eu ficava até tarde acordado sem razão? Is that okay?

Yes, it’s grammatically correct:

No passado, eu ficava até tarde acordado sem razão.

The differences are subtle:

ficava acordado até tarde (original)
– groups “stay awake” as a unit, then adds “until late”:
“I used to stay awake, [and that was] until late.”
ficava até tarde acordado
– puts more weight on “until late” right after the verb, then clarifies the state (acordado).
– Still understandable as “I used to stay up until late.”

Both are fine; the original (ficava acordado até tarde) is probably the most natural and fluid word order.

Why is it acordado and not acordada or something else?

Acordado is an adjective (or past participle used adjectivally) that must agree with the subject in gender and number.

Subject eu can be masculine or feminine, and Portuguese doesn’t mark gender in the pronoun here.
The form acordado assumes a masculine speaker.
A female speaker would say:
- No passado, eu ficava acordada até tarde sem razão.

Plural:

Nós ficávamos acordados… (group with at least one man)
Nós ficávamos acordadas… (all women)

So the ending -o / -a / -os / -as changes according to the subject.

Could I also say Eu costumava ficar acordado até tarde sem razão? What’s the difference from eu ficava acordado?

Yes, that’s perfectly correct:

Eu costumava ficar acordado até tarde sem razão.

Nuance:

Eu ficava acordado…
– imperfect tense alone already implies a past habit.
– very natural and common.
Eu costumava ficar acordado…
– uses costumar (“to be in the habit of”) + infinitive.
– Slightly more explicit and emphatic about the habitual nature:
“I used to stay up late” in a stronger “that was my habit” sense.

In many contexts they’re interchangeable; ficava acordado is often simpler and just as good.

Is there any difference between European Portuguese and Brazilian Portuguese in this sentence?

Grammatically, the sentence works in both varieties.
However, in Brazilian Portuguese, people might phrase it slightly differently in everyday speech:

Antes, eu ficava acordado até tarde sem motivo.
Antigamente, eu ficava acordado até tarde à toa. (very colloquial: à toa = “for no reason / doing nothing important”)

Key points:

ficava acordado até tarde is fine in both EP and BP.
sem razão is fine, though Brazilians often say sem motivo or à toa in casual speech.
The rest of the structure is shared between both varieties; pronunciation and some vocabulary preferences differ.