Actually, I don't know what you mean about the crypto black day. After I check the comment maybe like a day with Bitcoin value become less, or whatever you mean about the crypto black day it is nothing, Bitcoin is an uncontrolled asset, you cant make a day like black day, every day is about demand and supply
It's likely that the price of bitcoin has became lower.
And if he's looking for that day, he should turn himself to the charts and see how much bitcoin has dropped after hitting the all-time high.
Bitcoin dropped from $64k to $51k as of writing.