The journal Chronobiology International has published a contribution from these professors highlighting a flaw in the computer program used in an original study from Stanford University. This study linked the seasonal time change to negative health aspects, both acute (heart attacks, strokes) and chronic (obesity), and advocated for the elimination of the time change in favor of permanent winter time.
The original work utilized data from the U.S. Centers for Disease Control and Prevention (CDC), correlating disease prevalences with annual circadian misalignment obtained from a computational biological model. The study concluded that misalignment was greater with the time change and lesser with permanent winter time.
The error detected by professors Martín Olalla and Mira involves an incorrect sign in the calculation of the difference between the local meridian and the reference meridian, which shifted the positions of the analyzed counties from east to west. This means the calculated circadian misalignments referred to erroneous locations, empirically invalidating the results until the calculations are redone.
The authors of the original study acknowledged the error but downplayed its significance. Following a recalculation, the new values do not support the claim that permanent winter time is better than permanent summer time. The difference in annual circadian misalignment between the two options is only 0.2 hours per year, equivalent to 2 seconds per day, with equal misalignments for both time schemes.
According to Martín Olalla, the nearly two-hour annual increase in circadian misalignment noted by the original authors may be attributable to the study's methodology, which uses absolute values. He believes the reported difference is neutral and that the practice of changing time optimally regulates the circadian rhythm.
Jorge Mira adds that, in any case, 2 hours per year represent a 20-second daily misalignment, or 0.02%, and it is difficult to see how these magnitudes can predict global health aspects. This error follows another correction published in PNAS in April 2026, and the professors note that the flaw is striking, as it is equivalent to making the Earth spin backward.
