In general, those are the times where the big players aren't trading.
Nothing rocket-science here really.
Below a non-exhaustive list of no-brainer events where I'm not trading at all:
- weekends
- bank holidays
- right during a major announcement (especially true for indices/forex/stocks)
- ...
Cryptocurrencies special case
We know that:
- 80% of Bitcoin are held on cold storage i.e. aren't traded
- Bitcoin dominance is generally over 50%
- Whales aren't trading during the weekend
From those elements, we can fairly assume that:
- volume/liquidity/volatility are likely to be very low (or at best fake)
- fake means we see a violent move up/down on small timeframe canceled out few hours/days after by another violent move in the opposite direction on a small timeframe
To conclude:
- have this in mind when trading crypto during the weekends
- reduce your usual position sizing and leverage as you're basically trading against pump/dump trading algorithms run by your brokers