The four-day work week has moved from radical idea to serious policy experiment. Companies from Microsoft Japan to Perpetual Guardian to Buffer have tested compressed or reduced schedules with remarkable results: maintained or improved productivity, higher employee satisfaction, reduced burnout, and lower turnover. This article reviews the evidence from global trials, examines different models (compressed hours vs reduced hours), addresses implementation challenges (customer coverage, meeting compression, workload redesign), and provides a step-by-step guide for organizations considering the transition.