what is the {start time} for {Magna Carta} has {heritage designation} as {Memory of the World} ?
When was the Memory of the World the Magna Carta?
When did the Magna Carta become the Memory of the World?
SELECT ?g WHERE { ?g property:heritage_designation resource:Memory_of_the_World . resource:Magna_Carta property:heritage_designation ?g . ?g property:start_time ?g }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q12519> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1435> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q473858> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q12519 p:P1435 ?s . ?s ps:P1435 wd:Q473858 . ?s pq:P580 ?value}