Learn Hardcore Finnish: Laitan tietokoneen asetuksista yötilan päälle kello kymmeneen mennessä. - I turn on night mode from the computer settings by ten o’clock.

the verb laittaa = to put, to place, to set, to turn on (a device/setting)
1st person singular, present tense: minä laitan = I put / I set / I turn on

Finnish normally uses the present tense for both:

actions happening now
actions happening in the future

So laitan can mean either:

I’m turning on… (now)
I will turn on… (later)

The future meaning is understood from context and adverbs like kello kymmeneen mennessä (by ten o’clock).

Why is it tietokoneen asetuksista and not something like tietokoneesta or tietokoneessa?

Tietokoneen asetuksista literally breaks down as:

tietokoneen = of the computer (genitive singular of tietokone)
asetuksista = from the settings (elative plural of asetus = setting)

So the structure is:

tietokoneen asetuksista = from the computer’s settings

You are not doing something to the computer itself (so not tietokoneesta / tietokoneessa), but rather you are changing something in its settings menu, i.e. from within the settings.

In everyday English we might say:

from the computer settings
in the computer settings

Finnish expresses this source/location idea with asetuksista (out of / from the settings).

Why is asetuksista in the form with -sta (elative)? Could it be asetuksissa instead?

Asetuksista is the elative plural (out of / from the settings).

asetuksissa = in the settings (inside them)
asetuksista = from the settings (from inside them)

In this sentence, asetuksista suggests:

you go into the settings and from there you turn on night mode.

You could say tietokoneen asetuksissa (in the computer’s settings), and it would also be acceptable in many contexts. The nuance:

asetuksissa – emphasises location: “in the settings”
asetuksista – emphasises source / from there: “(doing it) from the settings”

Both are understandable; asetuksista is very natural when talking about changing or enabling something via a menu.

What does the expression laittaa (jokin) päälle mean exactly?

The verb + postposition combination laittaa päälle is an idiomatic way to say:

“to switch on / to turn on” (a device, light, setting, mode, etc.)

Literally:

laittaa = to put / to place
päälle = onto, on top of (allative form of päällä = on, on top of)

So literally it’s like “to put something into an on position” or “put something on”.

Examples:

Laitan valot päälle. – I’ll turn the lights on.
Laita televisio päälle. – Turn the TV on.
Laitan yötilan päälle. – I’ll turn on night mode.

So in your sentence, laitan … yötilan päälle = I turn on night mode.

Why is it yötilan and not yötila or yötilaa?

Yötila (night mode) appears here as yötilan, which is:

genitive singular of yötila

Two reasons:

Object case (total object)
With verbs like laittaa, a completed / whole action often takes a genitive object (total object). You intend to fully turn on night mode, not just partially do something with it.
- Laitan yötilan päälle.
  → I (completely) turn night mode on.
Genitive before the postposition päälle
The postposition päälle (onto, on (top of)) normally takes its complement in the genitive:
- pöydän päälle – onto the table
- tuolin päälle – onto the chair
- yötilan päälle – onto night mode / into the on-position of night mode

So yötilan is both:

the object of laitan, and
the required genitive complement of päälle.

What is the structure and meaning of kello kymmeneen mennessä?

Kello kymmeneen mennessä literally breaks down as:

kello = clock; o’clock (here: “at … o’clock”)
kymmeneen = to ten (illative case of kymmenen, ten)
mennessä = “by (the time [something] goes/reaches)”

So literally:

kello kymmeneen mennessä ≈ by the time it reaches ten o’clock
In normal English: by ten o’clock

The verb form mennessä comes from mennä (to go); it’s a special infinitive form that in time expressions corresponds to the preposition by:

viiteen mennessä – by five
jouluun mennessä – by Christmas
kello kymmeneen mennessä – by ten o’clock

Why is it kymmeneen and not kymmenen in kello kymmeneen mennessä?

Kymmeneen is the illative form of kymmenen (ten).

Illative often expresses movement toward a goal (“into / to / up to”). With mennessä, it indicates an end-point in time:

kymmeneen mennessä – by (up to) ten
viiteen mennessä – by (up to) five

If you used kymmenen (plain genitive/nominative) instead of kymmeneen, it would be ungrammatical in this construction. The verb form mennessä requires the illative for the time limit.

What is mennessä exactly? Why does “to go” appear in a time expression meaning “by …”?

Mennessä comes from the verb mennä (to go). It is an infinitive form that literally means “when going” / “in the course of going”, but in fixed time expressions it functions like the English preposition “by”.

Pattern:

[time expression in illative] + mennessä = by [that time]

Examples:

kymmeneen mennessä – by ten
viikkoon mennessä – by (within) a week
jouluun mennessä – by Christmas

So kello kymmeneen mennessä is just a more detailed version: by ten o’clock.

Could I say ennen kymmentä instead of kello kymmeneen mennessä? What’s the difference?

Yes, you can say ennen kymmentä, and it’s correct. The meanings are close but there’s a nuance:

ennen kymmentä
- literally before ten
- sounds like “at some unspecified time before ten; just not after it”.
kello kymmeneen mennessä
- by ten o’clock
- feels slightly more like a deadline: anytime up to and including that point (but practically it implies no later than ten).

In most everyday contexts, they overlap and both are fine:

Laitan yötilan päälle ennen kymmentä.
Laitan yötilan päälle kello kymmeneen mennessä.

The kymmeneen mennessä version sounds a bit more “formal deadline / by that time”.

Can the word order be changed, for example Kello kymmeneen mennessä laitan yötilan päälle…?

Yes. Finnish word order is relatively flexible, especially for adverbials like time expressions.

All of these are grammatical and natural, with slightly different emphasis:

Laitan tietokoneen asetuksista yötilan päälle kello kymmeneen mennessä.
→ Neutral, verb first, time at the end.
Kello kymmeneen mennessä laitan tietokoneen asetuksista yötilan päälle.
→ Emphasises the time limit “by ten o’clock”.
Laitan yötilan päälle tietokoneen asetuksista kello kymmeneen mennessä.
→ Same meaning; minor change of information order.

As long as the case endings stay correct, different orders mostly change what is emphasised, not the core meaning.

Is tietokoneen asetuksista the object of the verb, or is yötila the object?

The real object of laitan is yötila (appearing as yötilan):

laitan yötilan päälle – I turn night mode on.

Tietokoneen asetuksista is an adverbial phrase telling you from where / in which settings you do this:

tietokoneen – “the computer’s” (possessor)
asetuksista – “from the settings”

So the roles are:

Object: yötilan (night mode)
Location/source adverbial: tietokoneen asetuksista (from the computer’s settings)

Could I omit parts like tietokoneen asetuksista or kello and still be correct?

Yes, and this is common in real speech.

Omitting tietokoneen asetuksista
- Laitan yötilan päälle kello kymmeneen mennessä.
  → I’ll turn on night mode by ten o’clock.
  The sentence is still fully grammatical; it just no longer specifies where you are turning it on (phone, computer, tablet, etc.).
Omitting kello
- Laitan yötilan päälle kymmeneen mennessä.
  This is also understandable and often used. It still means by ten, though kello makes it extra clear that you’re talking about time of day.

In natural Finnish, people often leave out predictable details if the context already makes them clear.