The Milankovitch theory has long positioned boreal summer insolation as the key pacemaker of orbital-scale climate change. While this framework successfully explains glacial–interglacial cycles at high latitudes, absolutely dated proxies reveal a persistent "low-latitude puzzle": tropical precipitation variability is often asynchronous with hemispheric summer insolation, a pattern difficult to explain within the existing paradigm. Here, we argue that this puzzle is not merely a technical issue of asynchrony, but reflects a deeper epistemological limitation embedded in the Milankovitch framework itself. Developed within a high-latitude academic tradition and organized around the Gregorian calendar, a tropical-year system designed for obliquity-driven and temperature-dominated climates, the theory reasonably privileges boreal summer as the governing seasonal window. However, for low-latitude regions dominated by wet-dry seasonality, temperature and the boreal summer are not particularly important. Physically, at low latitudes, solar elevation angle and day length, relying on obliquity, vary little across both seasonal and orbital timescales, diminishing the dominance of obliquity-driven climate change. Instead, variation in Earth–Sun distance (precession × eccentricity) becomes proportionally dominant, especially on orbital timescale. Considering that low-latitude climate is governed by the Intertropical Convergence Zone (ITCZ), and that convective precipitation develops where the heating is greatest, it is reasonable to expect that orbital-scale low-latitude precipitation follows the strongest Sun (i.e., perihelion), with anomalistic year as its natural timeframe. This framework explains the observed asynchrony with hemispheric summer insolation and offers a more plausible physical basis for understanding orbital-scale climate variability in the low-latitude areas.

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