Thing → Intangible → Period
A (fairly vague) period of time, such as the Middle Ages, the Elizabethan age, lunchtime, etc..
Usage: Between 0 and 1 domains.
A fairly vague period, periods, age, or ages, usually associated with a particular stage of cultural development. Names may include the Elizabethan age, the 19th century (which ran from 1788 to 1914 in English history), or whatever is appropriate.
struct Period : Thing { };