You can easily buy Bitcoin on any online exchange, for example on
https://www.trustchange.com/ at any time of the day in services that centrally exchange digital assets. These resources have their own reserves at their disposal, at the expense of which transactions are carried out, and work on the principle of banks. The user selects a currency pair, specifies the amount, transfers the asset for sale to the service account, and in return receives the desired cryptocurrency or amount in fiat, depending on the direction of exchange. They are easy to use, reliable, but do not always offer favorable conditions.