Two different implementations might make two different local times out of that, e.g. due to not being aware of changing DST/timezone policies. Hence the recomme

Two different implementations might make two different local times out of that, e.g. due to not being aware of changing DST/timezone policies. Hence the recommendation of separating between user/clock/calendar time (which must be exact to a human) and absolute/relative timestamps (which must be exact to a computer).