what is the {start time} for {Leon Lai} has {spouse} as {Gaile Lok} ?
When did  Leon Lai and Gaile Lok's marriage take place?
When did Leon Lai and Gaile Lok marry?
SELECT ?n WHERE { ?m property:start_time ?n . ?m property:spouse resource:Gaile_Lok . resource:Leon_Lai property:spouse ?m }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q16836> .
?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/Q5517183> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q16836 p:P26 ?s . ?s ps:P26 wd:Q5517183 . ?s pq:P580 ?value}