Temporal Queries

SELECT ?decade (COUNT(?lang) AS ?count)
       (GROUP_CONCAT(DISTINCT ?langLabel; SEPARATOR=", ") AS ?languages)
WHERE {
  ?lang wdt:P31 wd:Q9143 ;
        wdt:P571 ?inception .
  BIND(FLOOR(YEAR(?inception) / 10) * 10 AS ?decade)
  SERVICE wikibase:label {
    bd:serviceParam wikibase:language "en" .
  }
}
GROUP BY ?decade
ORDER BY ?decade

SELECT ?century (COUNT(?site) AS ?count)
WHERE {
  ?site wdt:P1435 wd:Q9259 .  # UNESCO World Heritage Site
  ?site wdt:P571 ?inception .
  BIND(FLOOR((YEAR(?inception) - 1) / 100) + 1 AS ?century)
  FILTER(?century > 0)  # Only AD dates
}
GROUP BY ?century
ORDER BY ?century

SELECT ?era (COUNT(?city) AS ?count)
       (SAMPLE(?cityLabel) AS ?example)
WHERE {
  ?city wdt:P31/wdt:P279* wd:Q515 ;  # city or subclass
        wdt:P571 ?founded .
  BIND(YEAR(?founded) AS ?year)
  BIND(
    IF(?year < -500, "Ancient (before 500 BC)",
    IF(?year < 500, "Classical (500 BC - 500 AD)",
    IF(?year < 1500, "Medieval (500 - 1500)",
    IF(?year < 1800, "Early Modern (1500 - 1800)",
    IF(?year < 1900, "Industrial (1800 - 1900)",
    "Modern (1900+)")))))
  AS ?era)
  SERVICE wikibase:label {
    bd:serviceParam wikibase:language "en" .
  }
}
GROUP BY ?era
ORDER BY ?era