what is the {start time} for {The Apprentice} has {executive producer} as {Mark Burnett} ?
At what time did Mark Burnett start as executive producer for the Apprentice?
Tell me when  Mark Burnett, executive producer started for the Apprentice?
SELECT ?l WHERE { ?n property:start_time ?l . ?n property:executive_producer resource:Mark_Burnett . resource:The_Apprentice property:executive_producer ?n }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q863122> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P1431> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q3294019> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q863122 p:P1431 ?s . ?s ps:P1431 wd:Q3294019 . ?s pq:P580 ?value}