While uncertainty relations in quantum mechanics are based on non commuting
operators, the energy-time "uncertainty" is an exception since time is
a (classical) parameter.
There have been many unsuccessful attempts
to construct a general "time operator" which would give the energy-time
uncertainty the same operator based justification as the other uncertainty
relations.
Here, we accept that the energy-time uncertainty is for some reason not as
fundamental as the operator based uncertainties and we find a reason by
arguing that time is a useful but "man-made" concept which actually
arises from separation in space. Without resorting to relativistic
arguments we can construct the time-dependent Schroedinger equation from
the time-independent one by separation of system and environment in space
using a semiclassical approach.