The first entry is always the pin's source. Overall confidence is a weighted average of how firmly each reference supports the start and end times used above; a reference counts half as much for every 180 days older than the newest.
Happened as dated, per EA's press release: "Electronic Arts Inc. (NASDAQ: EA) today announced that the SimCity Cities of Tomorrow expansion pack is now available for PC and Mac at retail stores across North America and for digital download on Origin," dated November 12, 2013.
Wikipedia confirms the Cities of Tomorrow expansion "was released on November 12, 2013," matching the pin's stored date exactly.
PCR's own September 2013 preview states the expansion "will be available... on November 12th," corroborating the pin's stored release date two months ahead of launch.[1]
Something missing or wrong? Say it in your own words: a link that backs this pin up, a different start or end date and why, or a fact it lacks or gets wrong. The AI checks it against this pin's sources, searches for better ones, and adds any page that backs you up. The pin's own sources still count most.