what is the {start time} for {The Tonight Show} has {presenter} as {Johnny Carson} ?
Give the date Johnny Carson began as the presenter for The Tonight Show.
When did Johnny Carson start as the presenter for The Tonight Show?
SELECT ?h WHERE { resource:The_Tonight_Show_Starring_Jimmy_Fallon property:presenter ?z . ?z property:start_time ?h . ?z property:presenter resource:Johnny_Carson }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q1338655> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P371> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q310819> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q1338655 p:P371 ?s . ?s ps:P371 wd:Q310819 . ?s pq:P580 ?value}