What is {educated at} of {Barack Obama} that is {start time} is {1988-1-1} ?
On January 1, 1988, at which school was Barack Obama attending classes?
At which school was Barack Obama attending classes on January 1, 1988?
SELECT ?u WHERE { ?f property:start_time ?g . ?f property:educated_at ?u . resource:Barack_Obama property:educated_at ?f . FILTER ( CONTAINS ( YEAR ( ?g ) , '1988' ) ) }
select distinct ?obj  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q76> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P69> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj .
?statement <http://www.wikidata.org/entity/P580> <1988-1-1>
} 

SELECT ?obj WHERE { wd:Q76 p:P69 ?s . ?s ps:P69 ?obj . ?s pq:P580 ?x filter(contains(YEAR(?x),'1988')) }