Objective To assess the hypothesis that postoperative survival exhibits heterogeneity associated with the timing of quality metrics. Data Sources Retrospective observational study using the Nationwide Inpatient Sample from 2005 through 2009. Study Design Survival analysis was performed on all admission records with a procedure code for major cardiac surgery (n = 595,089). The day‐by‐day hazard function for all‐cause in‐hospital mortality at 1‐day intervals was analyzed using joinpoint regression (a data‐driven method of testing for changes in hazard). Data Extraction Methods A comprehensive analysis of a publicly available national administrative database was performed. Principal Findings Statistically significant shifts in the pattern of postoperative mortality occurred at day 6 (95 percent CI = day 5–8) and day 30 (95 percent CI = day 20–35). Conclusions While the shift at day 6 plausibly can be attributed to the separation between routine recovery and a complicated postoperative course, the abrupt increase in mortality at day 30 has no clear organic etiology. This analysis raises the possibility that this observed shift may be related to clinician behavior because of the use of 30‐day mortality as a quality metric, but further studies will be required to establish causality.