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