It's a global clock. UTC is the same time in Miami as it is in Singapore.
The accuracy of the delivery of that timesource is 10ns in theory, and upto 1000ns in practice.
The accuracy of the delivery of that timesource is 10ns in theory, and upto 1000ns in practice.
But UTC is ultimately defined by consensus. We need a reference clock and we need to be able to measure or estimate our skew in order to sync to it.