Connotation joke: the countryside holds literacy meeting, and the teacher explains the relationship between heaven and earth;

This is a joke with connotation, which involves the meaning of "day" and "day" in Chinese.

In Chinese, "day" is usually used to indicate a specific date or time, for example, "Tomorrow is Sunday". On the other hand, "day" is often used to express uncertain and vague time, such as "one day has passed" or "five days later".

The background of this joke is that at a rural literacy conference, the teacher tried to explain the relationship between "day" and "day" to the villagers. What the teacher may want to express is that "day" is a specific unit of time, while "day" is a more vague and less specific unit of time. However, since "Japanese" and "Japanese" both correspond to English "Japanese" in Chinese, this explanation may be confusing. Therefore, the humor of this joke lies in this unexpected and somewhat ironic explanation.