While historians employ diverse methodologies, they commit themselves to one core proposition: sensitivity to time is essential for a clear understanding of both stability and change. The discipline of history does not simply study or use past evidence. Good history requires understanding of what people at a given time in a specific place understood about their own world as well as an analytic understanding of processes of which historical actors may have been unaware. Intensely and pervasively alert to time’s role in shaping the present and future as well as the past, in our scholarship and in our teaching we aspire to help our readers and students understand that social, political, cultural, economic and other structures rest on relationships subject to alteration and movement over time. This sensitivity can play an important role in policy as well as more academic discussions. To isolate the role of time, historians – from most junior to most senior – read broadly to compare developments over varied chronological scales and culturally diverse societies. Although only occasionally directly addressed, historians do have a theory of time that contributes critical sophistication to the explanatory power of physical sciences, social sciences and professional disciplines as well as humanistic fields. Time is critical.