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Abstract Astronomical solutions form the backbone of accurate dating for geology and paleoclimate studies. Beyond 50 Ma, however, the chaos inherent in the solar system makes it impossible to calculate a unique astronomical solution. Geological data have been used to constrain the chaos in order to arrive at an astronomically calibrated time scale up to the end‐Cretaceous. Here, we adopt and extend this approach into the latest Cretaceous, by re‐analyzing the Zumaia and Sopelana composite proxy records from the Maastrichtian. We find that the filtered total light reflectance () record is most compatible with the astronomical solution ZB20a. However, the results are sensitive to parameter choices in our algorithm, which we describe in detail. Nevertheless, we present evidence in favor of using solution ZB20a for cyclostratigraphic applications during the latest Cretaceous. Intervals with very long eccentricity nodes (VLNs) (low amplitude in the short eccentricity cycle) in the astronomical solutions that coincide with large amplitudes in the short eccentricity‐related peaks in the filtered proxy record rule out alternatives.