The Working Hours Act
The Working Hours Act (Arbetstidslagen) regulates how much employees may work per day, per week and per year. In addition to regulating working hours in normal circumstances, it also deals with on-call time and preparedness. It also regulates the organisation of working time, dealing with what breaks one has a right to, and what applies when it comes to night-time rest.
The Working Hours Act applies, with some exceptions, to all work carried out in Sweden. It has provisions for full time work and part time work.
The Working Hours Act can be replaced, or partially replaced, by collective agreements. You can contact your local trade union for more information.
You can find the official text of the law here and an unofficial English translation here.