In some of the scenes right after the shooting on Utøya begins, one of the employees who informs the prime minister of the shooting can be seen holding an iPhone 5. This model was not released until September 2012.
At the 12th minute we can see Breivik dressed as a cop getting in a grey Fiat Doblo van parked behind a grey Suzuki Vitara, the new model that was released and sold only starting with 2015. The action was set in 2011.
When Viljar is being operated the surgeon takes out the bone flap which shows the brain directly underneath it. However, the brain is covered by a thick membrane, the dura mater, which needs to be opened separately. Sometimes the dura can be cut together with the bone, by accident, but rarely all the way round and even more rarely in young people.
When the police find Breivik's computer with his manifest, Windows 10 UI elements are visible. Windows 10 was released roughly 4 years after the events of 22 July took place.
The Mercedes-Benz Sprinter driven by Breivik is facelift model, manufactured 2014-2017.
When Viljar is at the hospital on Svalbard, a sign saying "Matsalur" is visible. This is Icelandic for "cafeteria", showing that this part of the movie was filmed on Iceland.
When Viljar is in the sports arena, saying he has 8 weeks, there is a blue sign behind him reading SJÓVÁ. It's the name of a Icelandic insurance company, revealing that this scene is shot on Iceland.
Svalbard is depicted with numerous patches of pine trees but in reality the landscape is barren tundra.
Christin Kristoffersen celebrates being elected "Mayor of Svalbard". Svalbard is not a city with a mayor but an archipelago. She was elected mayor of the largest city on it, which is Longyearbyen.