what is the {point in time} for {Portsmouth} has {population} as {248440} ?
When did Portsmouth have a population of 248440?
SELECT ?value WHERE { wd:Q72259 p:P1082 ?s . ?s ps:P1082 ?x filter(contains(?x,'248440')) . ?s pq:P585 ?value}
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q72259> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1082> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <248440> .
?statement <http://www.wikidata.org/entity/P585> ?value. 
} 

What was the date when 248,440 people lived in Portsmouth?