What do the dates next to nearly all sections of the wall show?

The dates next to nearly all sections of the wall, particularly when referencing a historical structure such as the Great Wall of China or other landmark constructions, typically indicate the time periods during which those sections were built, repaired, or renovated. These dates give visitors and historians valuable information about the chronological development of the structure, revealing insights into the historical context, architectural styles, construction techniques, and the purposes these sections served during different dynasties or eras.

For example, different sections of the Great Wall of China were built by various Chinese dynasties over many centuries, with the majority of the existing wall coming from the Ming Dynasty (1368-1644). The dates would thus reflect the construction periods during the different dynasties' rule, showing the evolution and expansion of the wall over time.