Why doesn't the calendar on Apple's mobile phone show any festivals?

This is because the option to show holidays in China is not turned on.

Taking the iPhone 7 mobile phone as an example, the method of opening the calendar to display holidays in China is as follows:

First open the iPhone 7, then find the "Calendar" item on the desktop of the iPhone 7, and click Enter.

2. After entering the calendar interface of iPhone 7, find the "Calendar" item at the bottom of the page and click Enter.

3. After entering, find the item "China Holiday", tick it, and then click "Finish" in the upper right corner of the page.