ATMs may be designed to use super precise timstamps, but they don't need to be. At all.
The interesting timing constraints are between stock exchanges... but in those situations the speed of light is a bigger factor than clock drift, even if you're just using NTP, and you can't avoid speed of light delays/desyncs.
Good point of view. From an ATM point of view, there is no need to rush other than verifying the user authenticity and available funds. Any double/triple/quadruple requests to withdraw funds within a short amount of time can be delayed since they would likely indicate malicious actors.
For stock exchanges you are absolutely correct. I remember many years ago paying so much extra for the fastest internet access and sub-second delay access to our local stock exchange. Even so it was still slower (lag) when compared to those with offices placed very close to the stock exchange building/infrastruture at that time.
ATMs may be designed to use super precise timstamps, but they don't need to be. At all.
The interesting timing constraints are between stock exchanges... but in those situations the speed of light is a bigger factor than clock drift, even if you're just using NTP, and you can't avoid speed of light delays/desyncs.