"Hon skrev fyra böcker på fem år."

Translation: She wrote four books in five years.

[yipivan]

Why på? (If it can ever be explained...)

[King2E4]

It can't be explained. Can you explain why we are ' at the library' when we are inside? Why are we 'in a car' but 'on a plane/train'? Why can we say both 'at the beach' and 'on the beach' with little to no difference in meaning?

It's just how prepositions work. That's the only explanation you will ever get from anyone.

[HenkSpaan2]

But surely someone might explain the intention of på. Is it four 'in every' five years? Or should you think of it as 'on the period'? In dutch the equivalent of på may in cases be translated to per.

You be anyone, methinks for meself.

Also note that to explain means to clarify. A single word can sometimes explain a universe of thought.

[Nicholas998236]

Scare George R. R. Martin with this sentence....

[CaNarsames]

I just love how Swedish can be as irregular as english!

[uxSY4nUr]

Can we say within five years?

[hans23950]

She is probably not related to George RR Martin.

[jbrains762]

Så... jag filmade fyra avsnitt av min videoutbildningsserie på en vecka? (eller finns det igen en skillnad med "en vecka"?)

[Lundgren8]

No, that’s fine. :)

[ZahraKarim0]

Kan du förklära skillnaden millan i år och på år

[this_is_Aryn]

I believe that i år is "it's going to happen in a year" and på år is "is going to happen throughout the year"

[AmbassadorTigger]

"I år" is "this year".

[Kanwal_Raj]

Hon skrev fyra böcker i fem år

Är det här också bra

[CedSgm7N]

Oh Great! Another unfamiliar use of the word "pa." I swear that word will be the death of me yet !!!!!!!

[Firemaster16]

According to rivstart b1+b2 textbok, when you use på in a time related sentence, it means how long the person took to complete the task, e.g. "Jag springer 5 kilometer på 30 minuter" (the example they gave).

I guess the English assumption would be to use "i 30 minuter" here instead, but that is used to mean how often or how long, e.g. "jag tränar en gång i månaden" (how often) or "jag tränar i 20-40 minuter" (again how long, but more generic - this is where we would use "for" instead of "in" as the preposition).

The distinction rivstart makes is that the first example is more how fast you do something - it's a well defined action happening at a specific time that you manage to complete at a certain speed. Whereas the last example is a vague action like exercising that happens more than once and where you are not so much completing a task but just repeating it for a certain amount of time. (These are all rivstart examples btw, sorry I couldn't provide a link)

Hope that helps somewhat.