China ancient astronomical calendar

A standard watch is not a complicated instrument. To put it bluntly, time is judged by the direction of the sun's shadow, and solar terms are judged by the length of the sun's shadow.

Let's talk about judging the solar terms by the length of the shadow. The length of the shadow is determined by the height angle of the sun. The higher the sun, the shorter the shadow. The solar altitude angle is higher in summer and lower in winter. Correspondingly, the shadow is shorter at noon in summer and longer at noon in winter. At a specific observation point, the noon height angle of the sun in a specific solar term is a specific value, and the length of the shadow is determined accordingly. So as to judge the solar terms.

The second is to judge the time by the position of the shadow, and the principle is also very simple. The direction of the shadow is opposite to that of the sun. In the morning, the shadow is in the west, in the afternoon, the shadow is in the east. However, due to different solar terms and different latitudes of the sun, the direction of the sun will be different at the corresponding time, which will lead to changes in the direction of the shadow. When observing, you should know the current date, find the corresponding scale, and then find the time point projected on the ground.

The standard is not complicated at all. Tianhuangping (a good place for astronomical observation in Jiangnan) has a standard. If the understanding ability is acceptable, 10 minutes can explain clearly how to look at the time and judge the solar terms through it. For people with a certain foundation like me, it is natural to know the meaning of various coordinates at a glance.

As for China's ancient calendar, it doesn't help the landlord's request. If there is a standard table in Meng Qian Bi Tan, it is similar (similar to an encyclopedia). But the specific calendar will not have such content (perpetual calendar+calendar making principle, similar to reference book+monograph).

One more thing, I can't say how good my knowledge of literature and history is, but at least it's above average, so it's not a problem to read Tang poetry and Song poetry, but when I turn to the twenty-four histories, I can only say that I'm ignorant ... Those books, let alone proper nouns, are literal contents. I guess the landlord is at a loss.

If you are really interested, you can have a look at Baidu Encyclopedia. If you can understand it, you can already lay a basic framework:

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