Common sense tells us that when it comes to learning, time matters. An individual simply cannot become more proficient in any given area without committing a certain amount of time to grasping new content, practicing and honing skills, and then applying knowledge and skills to realizing specific aims. Think of the chess master who plays match after match to improve his game or the scientist who toils long hours in her laboratory to unlock the mysteries of an intricate phenomenon. For them, becoming more adept in their chosen field is the result, in large part, of the time they invest. The great irony is that, for the better part of a century, our nation's public school system has, by its rigid adherence to the conventional calendar of 180 six-and-a-half-hour days, essentially disregarded the fundamental connection between time and learning. So what happens when schools and students are provided significantly more time for learning? As this review will highlight, both research and practice indicate that adding time can have a meaningfully positive impact on student proficiency and, indeed, upon a child's entire educational experience. The evidence makes clear that expanded time holds this potential because more time confers three distinct, though overlapping, benefits for both students and teachers: (a) More engaged time in academic classes, alongside broader and deeper coverage of curricula; (b) More time devoted to enrichment classes and activities that enhance students' educational experiences and engagement in school; and (c) More dedicated time for teacher collaboration and embedded professional development that together enable educators to strengthen instruction and develop a shared commitment to high expectations. In this paper, the authors explore these three benefits, which emerge as a longer school day and year open up new learning and growth opportunities. They consider evidence that demonstrates how time relates to each of the three, using a mix of form research studies and qualitative data from the field. As much as this evidence underscores the value that more time in schools can bring, it also makes clear that time is a resource that must be used well to realize its full potential. Absent intentionality of purpose and the deliberate pursuit of high quality, the power of more time will simply lie dormant. (Contains 2 tables, 2 figures and 52 notes.)