That appears to have been on December 7, 2017, when the price of Bitcoin rose over $2500 in a single day. > “Today Bitcoin surged past the $14000 ...
source https://www.google.com/url?rct=j&sa=t&url=https://www.quora.com/What-was-the-largest-recorded-single-day-gain-of-a-cryptocurrency&ct=ga&cd=CAIyGmM2Nzk3ODA2ZWViNjVjODI6Y29tOmVuOlVT&usg=AFQjCNGMfga3eQZbKG9Ml-vGHC0wd5HWfA
