What is {head of government} of {Montreal} that is {start time} is {2002-1-1} ?
Did the head of Government for Montreal start in 2001-1-1
SELECT ?obj WHERE { wd:Q340 p:P6 ?s . ?s ps:P6 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'2002')) }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q340> .
?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> ?obj .
?statement <http://www.wikidata.org/entity/P580> <2002-1-1>
} 

when was a  the head of Government for Montreal start in 2001-1-1?