Question: When did Chiang Mai become the sister city of Saitama Prefecture?
Paraphrase: When did Chiang Mai gotten to be the sister city of Saitama Prefecture?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q52028 p:P190 ?s . ?s ps:P190 wd:Q128186 . ?s pq:P580 ?value}