what is the {start time} for {George Hamilton-Gordon, 4th Earl of Aberdeen} has {position held} as {Prime Minister of the United Kingdom} ?
On what date became George Hamilton-Gordon, 4th Earl of Aberdeen,  the Prime Minister of the UK?
When was George Hamilton-Gordon, 4th Earl of Aberdeen as the Prime Minister of the United Kingdom?
SELECT ?x WHERE { ?t property:position_held resource:Prime_Minister_of_the_United_Kingdom . ?t property:start_time ?x . resource:George_Hamilton-Gordon,_4th_Earl_of_Aberdeen property:position_held ?t }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q24631> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P39> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q14211> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q24631 p:P39 ?s . ?s ps:P39 wd:Q14211 . ?s pq:P580 ?value}