Today's I-Ching hexagram wasn't cast by anyone. It was scheduled — and the schedule is two thousand years old.
In the first century BCE, two scholars, Meng Xi and his student Jing Fang, looked at the newly standardized solar calendar and saw addressable space. They shipped 卦氣六日七分: "hexagram qi, six days and seven parts," assigning every hexagram in the book to a fixed window of the year.
The arithmetic is the tell. Four hexagrams get pulled out to anchor the solstices and equinoxes; their 24 lines map one-to-one onto the 24 solar terms. That leaves 60 to cover the rest. 365.25 ÷ 60 = 6.0875 days each: six days plus exactly 7/80 of a day. The remainders accumulate back into whole days, so the cycle closes with no gaps and no collisions.
It doesn't even start on Hexagram 1. The cycle opens at the winter solstice on 中孚 (Inner Truth, Hexagram 61) and runs the classical sequence from there.
So the hexagram of the day isn't a coin toss tied to when you open the app. It's deterministic, computed from the winter solstice, and it's been running without drift for two millennia.
> CRON 卦氣六日七分 · epoch: winter solstice · drift: none