what is the {start time} for {Forbes Burnham} has {member of political party} as {People's National Congress} ?
When was Forbes Burnham a member of the PNC?
Since when was Forbes Burnham a member of the People's National Congress?
SELECT ?d WHERE { ?h property:start_time ?d . resource:Forbes_Burnham property:member_of_political_party ?h . ?h property:member_of_political_party resource:People's_National_Congress }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q718256> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P102> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q647210> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q718256 p:P102 ?s . ?s ps:P102 wd:Q647210 . ?s pq:P580 ?value}