The authors advocate that students frequently lack fundamental numerical literacy on the order of millions or billions, and that this comprehension is critical to grasping key evolutionary concepts related to the geologic time scale, the origin and diversification of life on earth, and other concepts such as the national debt, human population growth, etc. Helping students understand the magnitude of geologic time: (1) strengthens student understanding of biological concepts; (2) illustrates not just when things happened but also how they are interconnected; and (3) identifies and addresses common misperceptions. (Contains 1 table.)