what is the {start time} for {Fidel Castro} has {partner} as {Natalia Revuelta Clews} ?
At what time was Natalia Revuelta Clews the partner of Fidel Castro.
When did was Natalia Revuelta Clews the partner of Fidel Castro.
SELECT ?x WHERE { ?r property:unmarried_partner resource:Natalia_Revuelta_Clews . ?r property:start_time ?x . resource:Fidel_Castro property:unmarried_partner ?r }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q11256> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P451> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q19516418> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q11256 p:P451 ?s . ?s ps:P451 wd:Q19516418 . ?s pq:P580 ?value}