Nobody should be using an API like time(2) or clock_gettime(2)+CLOCK_REALTIME to measure event durations with sub-second precision or accuracy, especially when controlling mechanical equipment. And I'd be absolutely surprised if anybody was when controlling equipment, at least in a regulated industry.

On unix this is what CLOCK_MONOTONIC is for; for one thing, the real-time clock can be reset at any time. Technically even CLOCK_MONOTONIC could jump forward. Real-time embedded systems either provide other timing APIs, or make additional guarantees about CLOCK_MONOTONIC's behavior.