Question: When did Chongqing and Mpumalanga become sister cities?
Paraphrase: At which point in time did Chongqing and Mpumalanga become sister cities?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q11725 p:P190 ?s . ?s ps:P190 wd:Q132410 . ?s pq:P580 ?value}