The current market price is unstable in the day as today. It was from $ 6,600 and dropped to $ 6200, so stopping losses in day is still a difficult thing to say. A few days ago I invested XLM at $ 0.3 per coin, but now it's down to $ 0.21 per coin.
There is even no best time at all, the market is 24 hours and accessible, which in this case, you only want to know what you are doing. Market can make a move at any time it pleases. It is a very volatile market, there will always be movements now and then, but if you are really considering trading daily, then you really just want to be sure you have the knowledge to pull it through, which to me is what is mostly important. For what it is worth, as long as you have the perfect strategy to pull it off and you have some pretty good experience, anytime of the day you make a trade, you will still be doing well.
The best time period in a day is that when you free and no other work to do. You can spend that time for bitcoin trading, because when are mentally free you will better focus on trading and will make good and right decisions on the right time.
Well, since the crypto space is all round the clock, including weekends, anytime you really want to trade, you will see a trade to always make. There is really no best time, there is just best strategy which is to have the knowledge to trade daily as well as the experience and then try as much as possible not to over stress yourself so much in doing so as you will always want to be in the right set of mind. Day trading is not an easy task and even though can be profitable; you really want to be sure you are ready for those intraday headaches.