what is the {start time} for {Rostock} has {country} as {German Democratic Republic} ?
In which year, did Rostack became a part of the German Democratic Republic?.
When did Rostack become a part of the German Democratic Republic?
SELECT ?c WHERE { ?q property:start_time ?c . ?q property:country resource:East_Germany . resource:Rostock property:country ?q }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q2861> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P17> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q16957> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q2861 p:P17 ?s . ?s ps:P17 wd:Q16957 . ?s pq:P580 ?value}