Sista förbrukningsdagen är idag.

It is a compound noun:

• förbrukning = consumption / use
• dag = day
• -en = the

So förbrukningsdagen literally means the consumption day or the use day, but in food-label language sista förbrukningsdagen is the standard idea of a use-by date.

So this is one of those cases where the natural English translation is not word-for-word.

Because Swedish usually puts the definite article at the end of the noun.

• dag = day
• dagen = the day

The same thing happens in compounds: the definite ending goes on the last part.

• förbrukningsdag = use-by day
• förbrukningsdagen = the use-by day

So the -en is doing the job that the does in English.

Sista means last or final.

In this kind of phrase, sista is the normal form used before the noun:

• sista dagen = the last day
• sista tåget = the last train
• sista chansen = the last chance

So sista förbrukningsdagen means the last use-by day / the use-by date.

That is a very common learner question.

Normally, Swedish often uses both:

• a separate definite word like den
• and a definite ending on the noun

For example:

• den stora bilen = the big car

But with words like första, sista, and nästa, Swedish often leaves out den, especially in fixed expressions, headings, notices, and label-style language.

So:

• sista förbrukningsdagen is very natural
• den sista förbrukningsdagen can also exist in fuller prose, but the shorter version is especially common in this kind of context

Because Swedish main clauses usually follow the verb-second rule.

In this sentence:

• Sista förbrukningsdagen = the subject
• är = the verb
• idag = today

So the order is:

subject + verb + time expression

That gives:

Sista förbrukningsdagen är idag.

You could also start with idag, but then the verb still stays in second position:

Idag är sista förbrukningsdagen.

Both are grammatical.

Yes, idag is very commonly written as one word.

You may also see:

• i dag

Both mean today. The one-word spelling idag is very common in modern Swedish.

Because translations are often idiomatic rather than literal.

Swedish uses dag in this fixed expression, but the natural English equivalent on packaging is usually:

• use-by date

So even though dag literally means day, the best English translation is often date.

No.

They are related, but not the same:

• sista förbrukningsdagen = use-by date
  After this date, the food should not be eaten.

• bäst före = best before
  After this date, the food may still be okay, but quality may be worse.

This difference is important on Swedish food packaging.

Yes, but then it means a use-by day/date, not the use-by day/date.

Compare:

• förbrukningsdag = a use-by day/date
• förbrukningsdagen = the use-by day/date

In your sentence, the definite form is needed, because it refers to a specific day: the product’s final allowed day of use.

Yes, or something very close to it.

On packaging, Swedish often uses short, official, label-like wording. So a phrase like sista förbrukningsdagen is very natural in that context.

You might also see it written more like a label:

• Sista förbrukningsdag: 20/9
• Sista förbrukningsdagen är idag

So the sentence sounds practical and realistic, especially on food packaging or in a notice about expiry.