Resveratrol increases stability of the PER2 clock protein in both fetal cardiomyocytes and cardiac fibroblasts, shifting circadian phase through adenylyl cyclase signaling pathways in heart muscle cells. The compound also modulates dexamethasone's effects on cardiac circadian timing. Remarkably, while both resveratrol and dexamethasone altered cellular clock phase, neither affected mitochondrial rhythmicity, suggesting these two fundamental biological timers can operate independently in developing heart tissue. This finding challenges the conventional view that cellular and mitochondrial clocks are tightly coupled. For cardiovascular health, the research reinforces resveratrol's potential benefits during fetal development, particularly relevant given maternal supplementation studies showing improved heart function outcomes. However, the clinical implications remain speculative since this used isolated fetal cells rather than whole organisms. The discovery of uncoupled circadian and mitochondrial rhythms represents a paradigm-shifting insight into cardiac development biology. Understanding how timing systems coordinate—or fail to coordinate—during fetal heart formation could illuminate mechanisms underlying adult cardiovascular disease and inform prenatal intervention strategies.