Students completing a time calculation exercise identified the International Date Line (IDL) as a conceptual source of confusion and poor performance. From the early 1950s to the present, various geography textbooks have promulgated misstatements involving the occurrence of midnight at the IDL. This condition's persistence and ubiquity manifests a widespread fundamental misunderstanding, providing an opportunity to (a) illuminate the low level of student success when solving an IDL-influenced problem, (b) present an overview of textbook error, (c) explore how the evolution of the standard time system led to IDL errors in geography textbooks, and (d) offer proof dispelling these misconceptions.