A quarter has 13 weeks, so if you do 2 week sprints and align them to start with a quarter, there is 1 week per quarter that is not accounted for. That week can be used for stuff outside of daily activities. It can be used for training, offsites, working on a pet project, etc. Its a good way to build time in the schedule for this type of thing. These types of breaks have tremendous long term value.