Cake Day was a event in the month of November 2014.
It was one of the rewards to a challenge that started on November 10, 2014. The goal was to get as many people to escape from prison as possible.
Because 1000 escapees were reached, Team 17 released a update on November 13, 2014 which added Cake Day. On Cake Day all prisoners got a cake which contained a random (often rare) contraband item.