what is the {point in time} for {Rotterdam} has {population} as {631155} ?
On what date did Rotterdam have a population of 631155?
When did Rotterdam have a population of 631155?
SELECT ?k WHERE { ?f property:point_in_time ?k . FILTER ( CONTAINS ( ?n , '631155' ) ) . ?f property:population ?n . resource:Rotterdam property:population ?f }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q34370> .
?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> <631155> .
?statement <http://www.wikidata.org/entity/P585> ?value. 
} 

SELECT ?value WHERE { wd:Q34370 p:P1082 ?s . ?s ps:P1082 ?x filter(contains(?x , '631155')) . ?s pq:P585 ?value}