what is the {point in time} for {Grand Canyon National Park} has {visitors per year} as {4.38839e+06} ?
Which year did Grand Canyon National Park receive 4388390 visitors ?
When did Grand Canyon National Park have 4388390 visitors per year?
SELECT ?u WHERE { FILTER ( CONTAINS ( ?g , '4.38839e+06' ) ) . ?q property:point_in_time ?u . resource:Grand_Canyon_National_Park property:visitors_per_year ?q . ?q property:visitors_per_year ?g }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q220289> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1174> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <4.38839e+06> .
?statement <http://www.wikidata.org/entity/P585> ?value. 
} 

SELECT ?value WHERE { wd:Q220289 p:P1174 ?s . ?s ps:P1174 ?x filter(contains(?x , '4.38839e+06')) . ?s pq:P585 ?value}