If we go deeper than our (actually my) understanding abilities, then we are at the level of an idealist. At this level, we are not confirmed whether material world really exists or not. Then we can theorize that time is just a mental construct.
But if we are not at this much level of depth, then we are at the level of a scientist who takes material world a reality.
At this level … time is not any physical thing. But however, time is the name of a physical phenomenon.
Physical events do occur before and after one another. Course of occurrence of physical events is a physical phenomena.
Some events are repetitive in nature and they occur at regular intervals. In normal conditions, regular interval between one kind of physical event can correspond to exact number of intervals between some other regular type physical event.
Time can only be measured by comparing the number of intervals of different regular type events.
Time is duration between events. Duration is measurable by comparing the number of intervals of different regular type events. And that physical duration is the time!
