query: SELECT ?era ?eraLabel (YEAR(?start_time) AS ?start) (YEAR(?end_time) AS ?end) ?namedLabel ?namedDescription WHERE {
  ?era wdt:P31 wd:Q6428674; wdt:P361 wd:Q130436; # eras of the history of Japan
    wdt:P580 ?start_time.
  MINUS { ?era wdt:P2348/wdt:P361 wd:Q130436 } # exclude sub-eras
  OPTIONAL { ?era wdt:P582 ?end_time }
  OPTIONAL { ?era wdt:P138 ?named }
  SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en" }
  } ORDER BY ?start DESC(?end)