Abstract: Development of Earth system science calls for new approaches to time measurement of geological processes. Up to now, the Earth's orbital parameters remain the only periodicities in geology subject to precise calculations and, therefore, may provide new scales for geochronology. The 400-ka long eccentricity is the most stable orbital parameter over the entire geological history and drives long-term periodical changes in the oceanic carbon reservoir through low-latitude processes, at least since the Cenozoic. Being extensively and easily recognizable in geological records, the 400-ka cycles are potentially the astronomical "pendulum" for the geological clock.