Although the banks may close during a holiday, money can still be sent and received, stores are still open and credit cards still transact.

The financial exchanges also go on holiday and that may change at some point and be like the forex market. (Crypto markets)

There has been talk of a one world government in the future (I'm not sure about it). And there may be a one world currency system, if so, I would assume that it would be on a blockchain.