Currently we have many ways to make script execution happen on every frame, but there is no easy and clean way to actually get the time elapsed between two frames (commonly referred to as delta time).
Yes, there are possibilities, but they are all messy and the engine already has it's own delta time calculation that would only need to be exposed via a scripting command.
An example of such command could be simply
_deltaTime = deltaTime;
And be used in things like:
_object setVelocity [_x, _y, _z + (_za * deltaTime)];