Utflyttingsdatoen står i oppsigelsen.

Because Norwegian very often makes compound nouns by joining words together.

Here, utflyttingsdatoen is built like this:

• utflytting = moving out
• dato = date
• -en = the definite ending, so the date

So utflyttingsdatoen means the moving-out date.

This is very normal in Norwegian. Where English often uses several separate words, Norwegian often prefers one compound word.

That -s- is a linking sound/letter used in many Norwegian compounds. It does not by itself add a separate meaning like possession in English.

So:

• utflytting
  • dato
• becomes utflyttingsdato

You just have to learn these compound forms as they come up, because sometimes Norwegian uses a linking -s-, and sometimes it does not.

In Norwegian, the definite article is often attached to the noun as an ending instead of being a separate word.

So:

• utflyttingsdato = a moving-out date
• utflyttingsdatoen = the moving-out date

And:

• oppsigelse = a notice / termination / resignation
• oppsigelsen = the notice / the termination / the resignation

So both nouns are definite here.

Yes, står literally means stands, but in Norwegian it is also often used in the sense of:

• is written
• is stated
• appears
• is given

So Utflyttingsdatoen står i oppsigelsen means something like:

• The moving-out date is stated in the notice
• The moving-out date appears in the notice

This is a very common use of stå in Norwegian when talking about written information.

Because Norwegian often uses stå for information that is written somewhere.

Compare the idea:

• Det står i brevet. = It says so in the letter. / It is written in the letter.
• Det står på nettsiden. = It says so on the website.

If you used er, it would sound more like you are only saying the date exists inside the notice, not that it is specifically written/stated there. So står is the natural choice.

Oppsigelse can mean different things depending on context, such as:

• a notice of termination
• a resignation
• a cancellation notice
• in housing contexts, a notice to end a tenancy

In this sentence, it most likely means the notice document where the moving-out date is written.

So the exact English translation depends on the situation, but grammatically it is simply the notice/termination notice.

This is normal Norwegian main-clause word order:

• Utflyttingsdatoen = subject
• står = verb
• i oppsigelsen = prepositional phrase

So it follows the usual pattern:

subject + verb + other information

That makes the sentence very straightforward and neutral.

I usually means in.

Here it means the date is written in the notice/document.

Norwegian often uses:

• i for something written in a document
• på for something written on a surface or sometimes on a website/page, depending on context

So i oppsigelsen = in the notice.

Yes, absolutely. That would sound natural too.

• står i oppsigelsen = is written/stated in the notice
• er oppgitt i oppsigelsen = is given/stated in the notice

The original sentence is very idiomatic and common, but er oppgitt is also a good formal alternative.

Yes, especially in practical or official contexts such as:

• renting
• contracts
• moving
• housing administration

It is a typical administrative compound noun. In everyday speech, people might also say things in a less formal way, but utflyttingsdato is completely normal and useful to know.