Í september og október verða dagarnir styttri, svo ég kveiki fyrr á lampanum.

Í is the preposition used here for in, so Í september og október means in September and October.

A few useful notes:

• With months, Icelandic often uses í to mean in.
• The month names september and október are usually not capitalized in Icelandic, unlike in English.

In Icelandic, names of months are normally written with lowercase letters, unless they begin a sentence.

So:

• september
• október

This is different from English, where September and October are capitalized.

Here í takes the accusative case, because it expresses time within a period: in September and October.

In this sentence:

• september
• október

have the same form in nominative and accusative, so you do not see a visible change.

This is very common in Icelandic: sometimes the case matters grammatically even when the word form does not visibly change.

Verða means become or get, while eru means are.

So:

• dagarnir verða styttri = the days get/become shorter
• dagarnir eru styttri = the days are shorter

In this sentence, the idea is a change over time, so verða is the natural choice.

Dagarnir means the days, while dagar means just days.

Icelandic usually adds the definite article to the end of the noun:

• dagar = days
• dagarnir = the days

So dagarnir is the plural noun dagar plus the suffixed definite article.

Because dagarnir is plural: the days.

The verb must agree with the subject:

• dagurinn verður = the day becomes
• dagarnir verða = the days become

So verða is the correct present-tense plural form here.

Styttri is the comparative form of stuttur (short), meaning shorter.

In predicate position after a verb like verða, the comparative often appears in a form that does not change much for number and gender in the way a basic adjective does.

So:

• Dagurinn verður styttri = The day becomes shorter
• Dagarnir verða styttri = The days become shorter

Here styttri works as the comparative predicate adjective.

Here svo means so, in the sense of therefore / as a result.

The sentence structure is:

• Dagarnir verða styttri = The days get shorter
• svo ég kveiki fyrr á lampanum = so I turn on the lamp earlier

So svo connects cause and result.

After svo, Icelandic can introduce a clause much like English so I...

This clause has normal main-clause word order:

• ég = subject
• kveiki = verb

So:

• svo ég kveiki fyrr á lampanum

If another element were placed first, Icelandic would often use verb-second order. But here the subject ég comes first, so the order is straightforward.

Kveiki is the 1st person singular present tense of kveikja.

So:

• ég kveiki = I turn on / I light
• þú kveikir = you turn on
• hann/hún/það kveikir = he/she/it turns on

In this sentence:

• ég kveiki fyrr á lampanum = I turn on the lamp earlier

Even though English might sometimes prefer I will turn on, Icelandic often uses the present tense for something habitual or generally true.

Yes. Fyrr is a comparative adverb meaning earlier / sooner.

It is related in meaning to snemma (early), but the form is irregular:

• snemma = early
• fyrr = earlier

So:

• ég kveiki fyrr = I turn it on earlier

This is similar to English irregular comparison like well → better rather than weller.

Because the verb expression is kveikja á e-u, which means to turn something on.

So Icelandic does not say this the same way English does. It is not:

• kveikja lampann

but rather:

• kveikja á lampanum

The preposition á is required by the verb, and it takes the dative here.

So:

• lampanum is the dative singular definite form of lampi (lamp)

This is one of the most important things to learn with Icelandic verbs: many verbs require a particular preposition and case.

In modern usage, kveikja á means turn on, switch on, or light, depending on context.

For example:

• kveikja á lampanum = turn on the lamp
• kveikja á kerti = light a candle

So in this sentence, with lampanum, the natural meaning is turn on the lamp.

Because á in the expression kveikja á e-u governs the dative case.

Here is the noun:

• lampi = lamp

And here is the form in the sentence:

• lampanum = the lamp in dative singular

So the case is not chosen freely; it is required by the fixed verb phrase kveikja á.

Yes, it can be.

Icelandic often uses the present tense for:

• general truths
• habits
• repeated events
• near-future or predictable situations

This sentence describes what happens in September and October as a regular seasonal pattern:

• the days get shorter
• so I turn on the lamp earlier

So the present tense sounds natural even though the meaning can include a future or recurring situation.

Yes. Icelandic word order is fairly flexible, though not completely free.

For example, you could also see:

• Dagarnir verða styttri í september og október...

But when a time phrase comes first, as in:

• Í september og október verða dagarnir styttri

it sounds very natural and gives time-setting emphasis right away.

Also notice the verb placement:

• Í september og október verða dagarnir styttri

The verb verða comes early, which follows the common Icelandic verb-second pattern in main clauses.