At that time, when an examiner was marking papers, he found that most scholars had written the date wrong.

When I asked the reason, I realized that scholars can only calculate the date according to the astronomical phenomena, so it is common to miscalculate a day or two.

So the examiner called the imperial court and asked imperial academy to compile an almanac every year and sell it to the scholars, so that they could master the time.

As a result, the almanac was awarded to the people by the court and became a folk almanac, which has been passed down to this day.