I would like to use my electronic boarding pass to access security and passport checks a bit too early: 15 hours before the flight.
Is this going to be accepted in Arlanda airport, Stockholm? I don't have any luggage to check in.
The reason is that, if I stamp my passport later, I may be staying in the coutry over what my visa allows.
Passing through Immigration doesn't mean you have left the country, or the Schengen area... When you enter the secure area, you're not in a no-man's-land, but still in Sweden. You'll leave Sweden when your flight does.
Since it's only one day, there may not be consequences on the spot, but next time you try to enter there maybe be difficulties.