Learn Hardcore Portuguese (Portugal): Hoje vesti uma saia longa para o jantar, ao contrário do fim de semana passado em que fui de calças. - Today I wore a long skirt for dinner, unlike last weekend when I went in jeans.

If the action is finished and located in a specific time (today, yesterday, last weekend, etc.), Portuguese normally uses pretérito perfeito, not tenho + particípio.

Tenho vestido would mean something like “I have been wearing (repeatedly, over time)”, which is not what this sentence means. Here it’s about one specific occasion (today).

Why is it vesti uma saia longa and not visti-me uma saia longa or visti-me de saia longa? Isn’t vestir-se usually reflexive?

Both vestir and vestir-se exist, but they’re used slightly differently:

vestir + direct object: to put a piece of clothing on someone (including yourself)
- Hoje vesti uma saia longa. – I put on a long skirt.
vestir-se: to get dressed (usually more general)
- Hoje vesti-me cedo. – I got dressed early.

If you name the specific clothing item, the natural pattern is often non‑reflexive:

Vesti uma saia longa.
Ele vestiu um casaco.

You can say visti-me de saia longa, but that usually sounds like “I dressed myself in a long skirt”, with a bit more emphasis on the outfit or disguise (like vestir-se de preto, vestir-se de padre). For everyday “I put on a skirt”, vesti uma saia is the normal choice.

Could I say Hoje usei uma saia longa instead of Hoje vesti uma saia longa? What’s the difference between usar and vestir?

Both are grammatically correct but not identical:

vestir = to put on (the act of dressing)
usar = to wear / to use (the state of having it on)

So:

Hoje vesti uma saia longa…
Emphasises the moment of putting it on for dinner.
Hoje usei uma saia longa…
Emphasises that throughout today (or for the event) you wore a long skirt.

In context, both can be understood as “I wore”, but vesti is a bit closer to “I put on (for dinner)”, while usei is more “I wore (as my outfit)”.

Why is the adjective after the noun: saia longa and not longa saia?

In Portuguese, the default position for descriptive adjectives is after the noun:

uma saia longa – a long skirt
um vestido azul – a blue dress

Putting the adjective before the noun is possible but:

often sounds more poetic / marked / emotional
sometimes changes or shades the meaning.

Uma longa saia could be used, but it has a more literary or stylistic feel and is less neutral than uma saia longa in everyday speech. For a straightforward statement, saia longa is the natural order.

Is there any difference between saia longa and saia comprida?

In everyday European Portuguese:

saia longa and saia comprida are often interchangeable: a skirt that is physically long.
Some speakers feel longa is slightly more “fashion/clothing register” (like English “long skirt”), while comprida is the very common general adjective for “long” (length).

In this sentence, saia longa is perfectly natural and maybe a bit more standard / neutral fashion‑like than saia comprida, but both would be understood the same way.

Why is it para o jantar and not para jantar? Are both correct?

Both are possible, but they’re not identical:

para o jantar – for the dinner (a specific meal/event)
- Refers to a concrete occasion: tonight’s dinner.
para jantar – for dinner / to have dinner in a more general, activity‑like sense.

In this context, para o jantar emphasises that particular dinner event (maybe a family dinner, a date, etc.). Para jantar would also be understood, but sounds a bit more generic (for the act of having dinner).

What does ao contrário de / ao contrário do literally mean, and how is it used?

Ao contrário de literally means “to the opposite of” → “in contrast to / unlike”.

ao = a + o (to + the)
contrário = opposite
de = of

In your sentence:

ao contrário do fim de semana passado…
do = de + o, so: ao contrário de o fim de semana passado → ao contrário do fim de semana passado
= unlike last weekend / in contrast to last weekend.

It’s a very common way to introduce a contrast between two situations.

Why is it do fim de semana passado and not no fim de semana passado?

They express different relationships:

ao contrário do fim de semana passado…
= in contrast to last weekend…
Here, de marks the thing being contrasted (“of last weekend”).
no fim de semana passado…
= on / during last weekend…
Here, em (→ no) would mark time / location in time (“during last weekend”).

So:

Ao contrário do fim de semana passado, hoje vesti uma saia longa.
Compared with last weekend, today I wore a long skirt.
No fim de semana passado, fui de calças.
Last weekend, I wore trousers.

Your sentence needs de because it’s governed by ao contrário de (“in contrast to”).

Why is it fim de semana passado and not passado fim de semana?

Adjectives like passado (last) typically come after the noun:

fim de semana passado – last weekend
ano passado – last year
semana passada – last week

Passado fim de semana is not correct here.

You can also say no último fim de semana (on the last weekend), but fim de semana passado is the more direct equivalent of “last weekend”.

In em que fui de calças, why is em que used instead of quando? Can I say …fim de semana passado, quando fui de calças?

Both are possible, with a small nuance:

em que fui de calças
Literally “in which I went in trousers”.
Very idiomatic, slightly more formal/structured, and directly ties the relative clause to fim de semana.
quando fui de calças
Literally “when I went in trousers”.
Also correct and natural; focuses a bit more on the time aspect.

So you can say:

…ao contrário do fim de semana passado em que fui de calças.
…ao contrário do fim de semana passado, quando fui de calças.

Both are fine. The original is a very normal written style.

Why is it fui de calças (from ir) and not something like usei calças or estava de calças?

In Portuguese, ir de + roupa is a common expression meaning “to go (to an event/place) wearing [clothes]”:

fui de calças – I went (there) wearing trousers
Ela foi de vestido. – She went in a dress.

Alternatives:

usei calças – I wore trousers (focus on wearing them, less on going to the event)
estava de calças – I was in trousers (focus on state, what you were wearing at that time)

Fui de calças nicely contrasts with visti uma saia longa para o jantar in terms of choice of outfit for that occasion:
Today, I went to dinner in a skirt; last weekend, I went in trousers.

Why is it de calças and not com calças? What’s the difference between ir de and ir com in this context?

Both ir de and ir com can be used, but there are clear preferences:

ir de [roupa] is the usual idiom for going somewhere wearing a certain outfit:
- fui de calças, fui de vestido, fui de casaco.
ir com [roupa] is possible, but less idiomatic and can sound slightly heavier or less natural.

So a native speaker will nearly always say:

Fui de calças. rather than Fui com calças.

Use ir de + roupa for “go in / go wearing” as your default pattern.

Why is it just calças and not umas calças or as calças, while we do say uma saia longa?

The difference is mostly typical usage with these nouns:

saia tends to behave more like a countable item: you usually think of one skirt, so:
- uma saia longa – a long skirt
calças is usually plural and understood as a type of clothing rather than a counted object in casual speech:
- fui de calças – I went in trousers / wearing trousers.

You can say:

umas calças – some trousers / a pair of trousers
(fui de umas calças pretas – I went in some black trousers)
as calças – the trousers (specific ones already known in context)

But when you’re talking generally about “wearing trousers” as opposed to “wearing a skirt”, just plain calças is very natural:
fui de calças vs vestei uma saia.

How do I know that fui here is from ir (“to go”) and not from ser (“to be”), since they share the same preterite forms?

Context decides:

fui can be:
- eu fui from ir (I went)
- eu fui from ser (I was)

With de + roupa, the natural verb is ir:

fui de calças = I went in trousers (went wearing trousers).

If it were ser, we would expect something like:

Fui professora durante muitos anos. – I was a teacher for many years.
Fui muito feliz lá. – I was very happy there.

Since “to be of trousers” makes no sense, and “go in trousers” is a fixed pattern, fui here can only be from ir.