Why AI-powered astrology tools get the core calculations wrong

A developer who spent a year building a BaZi (Four Pillars astrology) engine has analyzed several popular GitHub projects — some with thousands of stars — that package Chinese divination as AI Skills. The author argues that while interpretation is subjective and hard to fact-check, the underlying astronomical casting calculations have exactly one correct answer, and most implementations get them wrong. A key flaw is that many tools store solar term dates at day-level granularity in Markdown files, when the BaZi year actually turns at a precise minute-level astronomical event called Lichun, meaning people born on boundary days can receive entirely incorrect charts. Geographic longitude is also widely ignored: because China uses a single national timezone across four solar time zones, two people born at the same clock time in Shanghai and Ürümqi can have different hour pillars. The broader lesson, the author notes, is that LLMs asked to perform lookups or calculations will produce plausible-looking answers, and without a clear error signal in the domain, mistakes go undetected indefinitely.