There is a genre of prompt going around: paste your birth date and time into a chatbot and ask for your Korean saju (or Chinese BaZi) chart — the four pillars, the day master, the whole thing. The answers read beautifully. They are also, structurally, guesses.
I run a saju reading service, so I care about this for selfish reasons. But the failure mode is interesting on its own, because it is the quiet kind.
What a chart actually requires
A Four Pillars chart is not text. It is the output of a calendar function:
Map the birth instant onto the sexagenary cycle — a 60-step cycle of stem–branch pairs that has been ticking continuously for centuries. The day pillar is literally "which of the 60 is today", counted from a known epoch.
