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 the source: "the University of Tokyo completed excavation of the colossal cavern that will house the main detector volume of Hyper-Kamiokande" on July 31, 2025.
The press release confirms University of Tokyo crews completed excavating the Hyper-Kamiokande cavern - roughly 330,000 cubic meters of rock - "on July 31, 2025," matching the pin's stored date exactly, about six months behind original schedule.[1]
The page could not be fetched, but this Frontiers in Physics paper on Hyper-Kamiokande's construction status, published November 2024, predates the actual cavern completion described by the pin and offers only earlier-stage academic context rather than confirming the July 2025 date itself.
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