what is the {start time} for {Henan} has {capital} as {Zhengzhou} ?
When did Henan have Ahengzhou as its capital?
What was the time when Henan had Zhengzhou as its capital?
SELECT ?i WHERE { ?b property:start_time ?i . ?b property:capital resource:Zhengzhou . resource:Henan property:capital ?b }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q43684> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P36> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q30340> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q43684 p:P36 ?s . ?s ps:P36 wd:Q30340 . ?s pq:P580 ?value}