what is the {start time} for {Maximilian I, Holy Roman Emperor} has {spouse} as {Bianca Maria Sforza} ?
On what date did Maximilian I, Holy Roman Emperor, marry Bianca Maria Sforza?
When did Maximilian I, Holy Roman Emperor, marry Bianca Maria Sforza?
SELECT ?u WHERE { ?l property:spouse resource:Bianca_Maria_Sforza . resource:Maximilian_I property:spouse ?l . ?l property:start_time ?u }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q150726> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P26> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q161136> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q150726 p:P26 ?s . ?s ps:P26 wd:Q161136 . ?s pq:P580 ?value}