Learn Hardcore Norwegian: De giftet seg sivilt i sentrum i fjor. - They got married in a civil ceremony in the city center last year.

De giftet seg i fjor.
– Simple past. A finished event located in time (last year). Very normal with a specific time expression like i fjor.
De har giftet seg.
– Present perfect. Focuses on the result now: They have (now) gotten married. Often used when the time is not specified or not important:
- De har giftet seg nylig. – They have recently gotten married.

With a clear past time like i fjor, Norwegian strongly prefers the simple past:

De giftet seg i fjor. ✔
De har giftet seg i fjor. ✘ (sounds wrong in standard Norwegian)

What does sivilt mean here, and is it an adjective or an adverb?

In this sentence, sivilt means “civil(ly), in a civil ceremony”, i.e. not in a church.

Grammatically here, sivilt is used adverbially: it describes how they got married (by civil ceremony).

Related forms:

sivil – adjective (base form): civil
et sivilt ekteskap – a civil marriage (adjective)
De giftet seg sivilt. – They got married in a civil ceremony (adverbial use)

You could also say:

De giftet seg borgerlig. – another way of saying in a civil ceremony.

Is sivilt necessary, or can I just say De giftet seg i sentrum i fjor?

Sivilt is optional. Without it, the sentence is still correct:

De giftet seg i sentrum i fjor. – They got married downtown last year.

However, you then don’t specify how they got married (church, civil, etc.).
With sivilt, you clearly say it was a civil (non-religious, non-church) ceremony.

What exactly does i sentrum mean, and why is it i and not på?

I sentrum literally means “in the center”, and in everyday speech it usually means:

“in the city center / downtown”.

Examples:

Jeg jobber i sentrum. – I work downtown.
Butikken ligger i sentrum. – The shop is in the city center.

The preposition i is used because you are inside an area (the central part of the town).
På sentrum is not used in standard Norwegian in this sense.

Can the time expression i fjor be moved to other positions in the sentence?

Yes. Norwegian allows some flexibility with time and place adverbials. All of these are grammatical:

De giftet seg sivilt i sentrum i fjor.
De giftet seg sivilt i fjor i sentrum. (less common, but possible)
I fjor giftet de seg sivilt i sentrum. (fronting the time element)

Position 1 (at the end) is the most neutral and common in speech.
Position 3 is often used for emphasis on when it happened.

Why is it i sentrum i fjor and not something like i fjor i sentrum as the default order?

Norwegian tends to prefer the order:

Manner (how?)
Place (where?)
Time (when?)

In your sentence:

sivilt = manner
i sentrum = place
i fjor = time

So De giftet seg sivilt i sentrum i fjor follows the common pattern: > verb + manner + place + time

You can change the order, but this is the most neutral-sounding version.

Can I say De ble gift sivilt i sentrum i fjor instead of De giftet seg sivilt i sentrum i fjor?

You can say it, but it sounds less natural in everyday modern Norwegian.

De giftet seg sivilt i sentrum i fjor.
– The normal, idiomatic way to say They got married in a civil ceremony downtown last year.
De ble gift sivilt i sentrum i fjor.
– Grammatically possible, but sounds more passive/odd. Bli gift is typically used in fixed expressions like:
- De ble gift i ung alder. – They got married at a young age.

For standard usage, prefer gifte seg when talking about people getting married.

Why is it seg even though the subject is plural (De) and not something like “seg selv” or a plural form?

In Norwegian, the third-person reflexive pronoun is always seg for both singular and plural:

han gifter seg – he gets married
hun gifter seg – she gets married
de gifter seg – they get married

You don’t change it to show plural; seg already covers both.

You can say seg selv (themselves / himself / herself) for emphasis in other contexts, but not in the fixed verb gifte seg. You just say gifte seg, not gifte seg selv.

Why don’t you say something like De giftet hverandre instead of De giftet seg?

Norwegian does not say “marry each other” with hverandre the way English might. The natural expression is the reflexive gifte seg:

De giftet seg. – They got married. (literally “married themselves”)

Hverandre (each other) is used in other contexts:

De elsker hverandre. – They love each other.
De hjelper hverandre. – They help each other.

For marriage, the idiomatic structure is gifte seg, not gifte hverandre.

What’s the difference between å gifte seg and å være gift?

They express different things:

å gifte seg – to get married (the event, the act of marrying)
- De giftet seg i fjor. – They got married last year.
å være gift – to be married (the state of being married)
- De er gift. – They are married.

So giftet is a past tense verb, while gift is an adjective describing marital status.

Is there a difference between giftet seg and gifta seg that I sometimes see or hear?

Yes:

giftet seg – Standard Bokmål written form.
gifta seg – Informal / dialectal spelling (and also Nynorsk form: gifta seg).

In speech, many people pronounce it closer to gifta seg, even if they write giftet seg.
If you’re learning standard written Bokmål, use giftet seg in writing.