Fortune teller Cao Pi proclaimed himself emperor.

Because people who tell Cao Pi's fortune divide day and night into two days, according to this algorithm, Cao Pi can live to be 80 years old, but the birthday is different from the usual year, so Cao Pi actually only lives to be 40 years old.

First of all, whether Cao Pi died at the age of 40 or 80, we must affirm the fortune teller's superb prediction ability. This fortune teller is Zhu Jianping. Although we don't know much about this person, Zhu Jianping is indeed a person with very strong predictive ability, and he was also quite famous at that time. Fortune telling is a way of life for many people in ancient times, so it is often untrue. Fortune tellers usually use unpredictable signs, cheat everywhere and make money by some alarmist remarks, so most of them mention fortune telling, but Zhu Jianping is an exception.

Secondly, Zhu Jianping told Xelloss's fortune on a very grand occasion. At that time, North Korean ministers held a grand banquet, and many dignitaries gathered there. Zhu Jianping was invited to a banquet because of his good reputation for accurate fortune-telling, and then Cao Pi asked Zhu Jianping to divine for himself and some ministers present. Later, Zhu Jianping said at the banquet that Xelloss would be eighty years old, and finally mentioned that there would be great disaster when Xelloss was forty years old.

So, Zhu Jianping's prediction ability is not generally accurate. His predictions to ministers at the banquet have basically come true, and Cao Pi is no exception. Because when Zhu Jianping predicted to xelloss, he said he was eighty years old, not that he could live to be eighty years old, but that he meant to separate day and night into two days, so xelloss predicted that his life span was forty years old.

Finally, to sum up, Cao Pi died at the age of 40, not because the prediction failed, but because the prediction was based on longevity, and one day counts as two days.