Time was a fundamentally relative Concept.
The rate at which it passed was not constant, and it changed depending on various factors. One of those factors was the kind of universe one existed within.
For Primary Universes, the general speed at which time passed was slower relative to Secondary Universes.
Then, when it came to the interstitial space of the multiverse, where the immense gravities of the ginormous celestial bodies known as universes warped the fabric of space-time, the speed of time became even more unstable.
This was why, to avoid losing track of their perception, the average rate of time within a universe was usually what people within that universe used to calculate how much "time" they had spent outside it.
In a war spanning dozens of universes and thousands of battlefronts, where armies constantly travelled between different universes and fought across vast stretches of inter-universal territory, this distinction became increasingly important.
