I thought for fun I'd look at the weekly trends in BitCoin prices. I've heard people say that Wednesday's are a good day to buy, and Friday's are a good day to sell, and was curious whether this would be borne out in the data. So I downloaded data from 2016 onwards, from Coindesk's API, normalised it, and aggregated it by weekday, to make the below graph. Although there are big confidence intervals on the data, in general, it seems that Sunday's are the best day to buy, and Thursday's are the best day to sell.
I took this premise and tested it against the same dataset I made the graph from. I found that if you'd bought on a Sunday, and sold on a Thursday, 62% of the time you would make a profit.
Caveats to this .... I am not a statistical analyst, nor a financial advisor. This is my own analysis that I'm sharing, you should do your own if you want to use this for investment. This is not investment advise. Furthermore, my analysis is simplistic. It looks at daily prices, when prices actually change per hour, so is flawed in this regard. It also does not take account of volume of purchase/sale.
If you liked this little analysis, please upvote and I'll do similar for LiteCoin, Ethereum and some other popular crypto-currencies.