Learn Swedish: Det låg en faktura på skrivbordet i onsdags. - There was an invoice lying on the desk last Wednesday.

The structure i + day of the week + -s is used specifically to refer to a day in the past. It translates to "last Wednesday." If you used på onsdag, it would mean "on Wednesday," which usually points to the upcoming future.

Why is the verb låg used here to mean "was"?

When saying "there is" or "there was" about a physical object, Swedish usually prefers positional verbs rather than a generic word for "was." Because an invoice is flat and rests horizontally on the desk, it "lies" (ligger in present tense, låg in past tense) there. If it were an upright object like a coffee mug, you would use stod (stood).

Could I start the sentence with i onsdags instead?

Yes, you can! If you want to emphasize when the invoice was there, you can move the time phrase to the front. Just remember that Swedish is a verb-second language, so the verb låg must swap places with det: I onsdags låg det en faktura på skrivbordet.

Is låg related to the verb att lägga?