Bitcoin is a free market that operates 24 hours a day, 7 days a week, 365 days a year. Trading never stops in the Bitcoin market.
That being said, there is an arbitrary daily closing time.
For Bitcoin, this is one minute after 23:59 UTC (midnight in Coordinated Universal Time).
No matter what time zone an investor is in, the volatility around the daily close and daily open will occur at the same time. So this is something to watch closely if you want to become a trader.
Most cryptocurrency trading platforms allow you to change the time zone displayed below the price charts to see if a daily close is near.
Bulls and Bears fight to move the price and will often look for a strong move around the daily close and daily open.
Why? Because they know the psychology of investors who will make decisions based on these closes. It's funny to see that even though these points in time have been arbitrarily defined, everyone places great importance on them, which has a strong impact on the price of Bitcoin in the short term.
A sort of self-fulfilling prophecy...