History

History questions are mostly date arithmetic in disguise. How long something lasted is easier answered by subtracting two dates you know than by recalling a duration, and most of the endpoints in this category are among the better-known dates in European and world history.

The recurring correction is that names lie. A war named for a round number of years rarely lasted that long, a founding date is usually a legend given a calendar entry, and an era boundary is a convention historians chose afterwards. Where a question says 'actually', expect the label and the measurement to disagree.

Pre-modern figures are reconstructions rather than records. Populations, death tolls and durations from before systematic record-keeping are assembled from tax rolls, grain distributions and archaeology, and they have moved substantially as scholarship improved. The sources here are named so you can see how each number was built.