what is the {start time} for {Petah Tikva} has {twinned administrative body} as {Gabrovo} ?
When did Petah Tikva become the twinned administrative body of Gabrovo?
SELECT ?value WHERE { wd:Q190828 p:P190 ?s . ?s ps:P190 wd:Q180131 . ?s pq:P580 ?value}
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q190828> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P190> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q180131> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

on what date did Petah Tikva become the twinned administrative body of Gabrovo?