How we source and verify events

What a round is made of

Every playable round is one event with four pieces of data behind it: a location (latitude and longitude), a date, a written clue, and an explanation shown after you answer. The first two are sourced. The last two are written by us.

Coordinates and dates: Wikidata (CC0)

An event’s coordinates and its date are taken from Wikidata, the structured-data project maintained alongside Wikipedia. Wikidata is released under the Creative Commons CC0 1.0 public-domain dedication. This is the part of the game we can point at: when a round reveals that something happened at a particular place in a particular year, that place and that year came from a citable structured record, not from a model’s memory and not from us guessing.

Candidates are pulled through a scripted harvest pipeline rather than hand-typed, so a transcription slip cannot quietly enter the pool. Anything missing coordinates or a usable date never becomes an event at all.

Clues and explanations: our writing, grounded on Wikipedia (CC BY-SA)

The clue you read, and the “why here” and “why then” lines in the reveal, are original editorial written against our internal editorial policy. They are researched against the English Wikipedia article for the event, and where we have recorded which article that was, the reveal links to it so you can check us. English Wikipedia text is licensed CC BY-SA 4.0 — a different licence from Wikidata’s CC0, which is why we credit it separately here. We do not reproduce Wikipedia prose; we write our own and cite the article behind it. Roughly half the current library carries that recorded source link, and backfilling the rest is ongoing.

What “reviewed” currently means — honestly

Events are published at an approved status, which is what makes them eligible to appear in play. We are working through an editorial review pass over the library, and it is not finished. So we do not claim that a human has read and signed off every event now in the game, because that would not be true yet. What we do claim is narrower and checkable: the coordinates and dates are Wikidata-sourced, the writing is ours, and we remove events that fail our content policy as we find them.

If you find something wrong — a bad coordinate, a wrong year, a clue that gives the answer away, or an event you think should not be in a scored guessing game — tell us at hello@endpaperlabs.com and we will fix or remove it. Corrections are the fastest route into the review queue.

Dates we only know roughly

History is not uniformly precise, and pretending otherwise would be its own inaccuracy. We record how precisely the source knew each date, so a reveal can say “1876” when only the year is established rather than inventing a day and a month. Older eras skew this way heavily: an Antiquity round is scored against a much wider time tolerance than a 20th-century one for exactly this reason, and the timeline you answer on uses bands whose width changes era by era to match.

Pictures

Some events carry a photograph or an image in the reveal and some do not — a little under half of the library has one today. We would rather show nothing than illustrate an event with a picture of something else, so an event without a verified image simply does not get one.

Events we exclude

A guessing game grades you on how close you came, in kilometres and in years. There is material for which that framing is simply wrong, so the base pool excludes it: recent mass-casualty attacks within living memory, ongoing or unresolved conflicts, events in which children were deliberately targeted, and cases where guessing the location is itself the trivialising part. Military engagements between combatants, political assassinations, coups, and natural disasters are not excluded on those grounds. The automated harvest carries a recency floor so material of this kind cannot enter the pool unattended, and we are working back through what predates that rule.

Maps and other attribution

The basemap is derived from OpenStreetMap — © OpenStreetMap contributors, available under the Open Database License (ODbL) — and is built and served with MapLibre GL and Protomaps tooling (both BSD-licensed). Country, subdivision and physical-geography boundaries used in Geo Drills come from Natural Earth, which is in the public domain. Terra Tempus itself is proprietary software; none of the above is claimed as ours.