Approaching Midnight presents the history of the year 2000 technology problem (Y2K), exploring how the efforts to respond to the problem forced a broad societal reckoning with the essential role computers had come to play in daily life in the United States by the close of the twentieth century. While Y2K is at core about a technical issue arising from the mid-twentieth century programming decision to truncate dates in order to save on expensive computer memory, this historic account considers the ways in which Y2K ultimately became much more than just a technical problem. Presenting the history of Y2K through an engagement with the remediation work of information technology professionals, the assessments made by congressional committees, the publications from mass media outlets, and the activities of community preparedness groups—this dissertation investigates how different groups made sense of Y2K, and how they perceived and sought to prepare for what this computing crisis might bring. Pushing back on the condescension of hindsight that treats Y2K as little more than a techno-panic, Approaching Midnight focuses on the tremendous efforts that went into ensuring that Y2K would not result in calamity, while highlighting the uncertainty that fed into anxious appraisals. This dissertation argues that Y2K revealed society’s reliance on complex computer systems, while simultaneously revealing the fragility of those very systems.