what is the {start time} for {New York City} has {head of government} as {Robert F. Wagner} ?
is the {begin time} for {Unused York City} has {head of government} as {Robert F. Wagner} ?
is the {start time} for {New York City} has {head of government} as {Robert F. Wagner} ?
SELECT ?p WHERE { ?l property:head_of_government resource:Robert_F._Wagner . ?l property:start_time ?p . resource:New_York_City property:head_of_government ?l }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q60> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P6> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q439156> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q60 p:P6 ?s . ?s ps:P6 wd:Q439156 . ?s pq:P580 ?value}