what is the {start time} for {Tony Blair} has {position held} as {Leader of the Labour Party} ?
What year did Tony Blair become President of the Labour Party?
When did Tony Blair become the Leader of the Labour Party?
SELECT ?i WHERE { resource:Tony_Blair property:position_held ?l . ?l property:position_held resource:Leader_of_the_Labour_Party . ?l property:start_time ?i }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q9545> .
?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/Q3615378> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q9545 p:P39 ?s . ?s ps:P39 wd:Q3615378 . ?s pq:P580 ?value}