2/26/2016
🥷 First ZKCP Payment
On February 26, 2016, the first successful Zero-Knowledge Contingent Payment (ZKCP) was made on the Bitcoin network.
Sources:
https://archive.bitcoin-calendar.org/archive/1749203883.201389/index.html#singlefile.html
https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-announcement/