A light year is a measure of distance, not of time. It is the distance light travels in a year. But can you name a so-called measure of time that is not really a measure of distance? A year in ordinary time is the distance that it takes for the earth to make one revolution around the sun. Months, minutes, and seconds are divisions of this unit. They are merely increments of that unit of distance. We talk as though we know what time is. In truth, we are fish swimming in a sea that we cannot perceive. So we use these terms of time measurement which do not actually measure anything but space.
For to say that we have gone such and such a distance in so long a time is to say nothing more than that we have gone such and such a distance relative to another distance. If we are measuring time purely in terms of distance, we have no measurement of anything except space.
Ordinary units of space are not particularly meaningful in themselves, of course. A foot, a mile, and so on—these units are based on rough approximations which we have in latter days codified in arbitrary fashion. Spatial units of measurement are entirely relative, referring back and forth among themselves with no absolute meaning. You could argue perhaps that the Planck length describes something real and not arbitrary, but this is such a tiny unit (1.61 x 10-35 m) that it rarely figures in our calculations of, say, how far it is from our house to Bangor, Maine. (Those who live in Bangor, Maine, may, for the purposes of this example, substitute Ottumwa, Iowa).
My conclusion is that it's all space—what we ordinarily refer to as time, that is, in a misplaced metaphor. And space is nothing more than than the imagination that we can stand still long enough in this cosmos to fix a distance between two objects. (As if the concept of object had some meaning itself.)
To know real time and real space, we had better abandon all notions of time and space whatsoever.