what is the {start time} for {Marco Polo} has {spouse} as {Donata Badoer} ?
When Donata Badoer married Marco Polo
When did Marco Polo marry Donata Badoer?
SELECT ?q WHERE { ?u property:start_time ?q . ?u property:spouse resource:Donata_Badoer . resource:Marco_Polo property:spouse ?u }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q6101> .
?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/Q3713678> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q6101 p:P26 ?s . ?s ps:P26 wd:Q3713678 . ?s pq:P580 ?value}