This exploratory research report investigates whether the trans-Neptunian object 90377 Sedna may function as a long-term chronological marker associated with periods of large-scale planetary transition. The hypothesis advanced here does not propose that Sedna directly causes climate change, geological disruption, cometary influx, or civilizational transformation. At its enormous distance from Earth, such a direct causal mechanism remains unproven and should be regarded as speculative. Instead, this report examines Sedna primarily as a temporal marker: an astronomical body whose approximately 11,400-year orbital period may coincide with major transition windows in Earth history and in long-duration cyclical systems preserved by human cultures. The study adopts a chronological-comparative methodology. Sedna's orbital period and expected perihelion around 2075-2076 CE are compared with the Younger Dryas termination, selected ancient cyclical chronologies, and recurring cultural structures that describe world ages, renewals, and transitions. Because precise back-calculation of long-period trans-Neptunian objects across more than eleven millennia is affected by orbital uncertainty, cumulative gravitational perturbations, the object's extreme eccentricity, limitations in paleoclimatic dating, and the shifting observational framework associated with Earth's axial precession, a conservative analytical margin of +/-500 to 1000 years is applied throughout this paper. The central question is whether the repeated appearance of comparable 10,000-12,000-year timescales across independent systems represents coincidence, cultural convergence, collective memory, or a larger cyclic framework operating within the Solar System. Possible physical mechanisms, including barycentric dynamics, resonance effects, and cometary redistribution, are discussed separately as exploratory hypotheses and not as established explanations. The report concludes that the Sedna Chronology Hypothesis is not yet a causal model, but that its chronological pattern is sufficiently structured to justify further interdisciplinary investigation