You can in fact express this in terms of "seconds/second", as in how many seconds pass in some other reference frame for each second in yours. In that sense, the "speed of time" can in fact be meaningful.
Relativity provides a more rigorous way of modeling this, treating spacetime as a four-dimensional manifold. When you move through the spatial dimensions relative to some reference frame, the rate of your motion through time is reduced relative to that same reference frame. This is commonly modeled on a spacetime diagram: https://en.wikipedia.org/wiki/Minkowski_diagram
You can in fact express this in terms of "seconds/second", as in how many seconds pass in some other reference frame for each second in yours. In that sense, the "speed of time" can in fact be meaningful.
Relativity provides a more rigorous way of modeling this, treating spacetime as a four-dimensional manifold. When you move through the spatial dimensions relative to some reference frame, the rate of your motion through time is reduced relative to that same reference frame. This is commonly modeled on a spacetime diagram: https://en.wikipedia.org/wiki/Minkowski_diagram