what is the {start time} for {Richard Seddon} has {position held} as {mayor} ?
When did Richard Seddon start being mayor?
SELECT ?value WHERE { wd:Q559640 p:P39 ?s . ?s ps:P39 wd:Q30185 . ?s pq:P580 ?value}
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q559640> .
?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/Q30185> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

at what time did Richard Seddon begin being a mayor