We subscribe to an online encyclopedia to help one of my sons with homework, and because I placed the order, their “This Day in History” feature comes to my inbox. China rarely figures, which isn’t that surprising. After all, they need brief, punchy items that will catch readers’ attention, and that means items familiar enough to a general audience that a five word title is understandable, and that only three sentences are needed to remind us of what happened and why we should care. So I’m not crusading for “1644: Manchus enter Beijing with the help of Wu Sangui” to replace D-Day as the entry for June 6. Still, anniversaries are good hooks for thinking about how history matters, and Chinese history has plenty of them. From that perspective,...