Cyclostratigraphy claims to rely on an accurate astronomical time scale and further on a clear imprint it supposedly makes on the sedimentary record. Grounded upon the Milankovitch theory, geologists first sought to apply this method to develop a timescale for Quaternary glacial/interglacial oscillations. But there are several glaring unresolved problems with this approach. Although solar radiation measurements at high latitude appear to lend support to the mechanism, the data are carefully selected, typically restricted to the summer solstice or the months of June or July. By contrast, the larger dataset for the warm half-year for the whole hemisphere shows the Milankovitch effect is very small. Moreover, geologists believe glacial episodes over the past 900,000 years have been controlled by the 100,000-year eccentricity cycle, but that cycle has a very small effect relative to other cycles. Further, glacial cycles should be out of phase between the hemispheres, yet they are not. Finally, proponents rely on correlation between Milankovitch cycles and deep-sea cores, but these appear to be the result of circular reasoning and the reinforcement syndrome.