Most of what I can say about this subject is pretty much the same as for history in general, but more specific details are in the current round of development. The 16th century, the 17th century, the 18th century, and the 19th century all need more specific details before I can discuss them in any but the most general terms.
I've extended the 20th century a little further back. The Mid 20th century (1941-1960) includes most of World War II, a major event in world history, and the beginnings of the Cold War. I have broadened the connections of the late-mid 20th century (1961-1980) and the late 20th century (1981-present), but don't have enough detail to report on them yet.