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.
You're right the crypto market traded all round the clock but there are always the best time for everything, even with this current market situation there are best time to enter the market if you watch the price movement very well which I believe mid-night, early morning and the weekend are the most best time to start trading.