"In perfect void can we define time?"
First define time generally, define space (and hence voidness) generally, then you can attempt to answer :)
The variety of articulations of both time and space (sometimes intertwined as spacetime), is too large to encompass in a simple Phil.SE answer. @Jo gave the popularly scientifically accepted theories in history. But since you so clearly referenced "events" in your question, I'd like to add another theory, one inherently event-based.
I'll begin by providing Whitehead's criticism of Newtonian conception of space, and hence void:
Newton, basing himself upon current physical notions, conceived
'sensible objects' to be the material bodies to which the science of
dynamics applies. He was then left with the antithesis between
'sensible objects' and empty space. Newton, indeed, as a private
opinion, conjectured that there is a material medium pervading space.
But he also held that there might not be such a medium. For him the
notion 'empty space'—that is, mere spatiality—had sense, conceived as
an independent actual existence 'from infinity to infinity'. ...Newton
in his description of space and time has confused what is 'real'
potentiality with what is actual fact.
(Process and Reality, p.72-73)
Whitehead claims that because Newton inherently connects the actual world with the empirical actual facts, he had to conceive of a concept for 'empty space'. This, according to Whitehead, is what made the history of philosophy of nature to struggle so much with articulating non-occupied space.
Now to sort out Whitehead's attempt to provide an answer, I'll begin with some definitions.
Alfred N. Whitehead defines event as following[*]:
An event is a nexus of actual occasions inter-related in some
determinate fashion in some extensive quantum: it is either a nexus in
its formal completeness, or it is an objectified nexus.
... Where 'actual occasions' mean:
'Actual entities'-also termed 'actual occasions'—are the final real
things of which the world is made up. There is no going behind actual
entities to find anything more real... The final facts are, all alike,
actual entities; and these actual entities are drops of experience,
complex and interdependent.
It should be noted that for Whitehead there is a difference between "the world" and the "extensive continuum", which is what we usually call the universe.
But we need one more definition:
Actual entities involve each other by reason of their prehensions of
each other. There are thus real individual facts of the togetherness
of actual entities, which are real, individual, and particular, in the
same sense in which actual entities and the prehensions are real,
individual, and particular. Any such particular fact of togetherness
among actual entities is called a nexus (plural form is written nexūs).
I'll regard nexus as the primary type here, to avoid confusion with ordinary language. As defined, a nexus is actual occasions connected by facts or togetherness. If those connections are inherently of the kind of continuance, i.e. inheritance, then this nexus is an ordered nexus - i.e. a society. There are multiple kinds of societies, the one we refer to the most are the 'corpuscular societies'.
Yet another definition:
A 'society' in the sense in which that term is here used, is a
nexus with social order; and an 'enduring object' or 'enduring
creature' is a society whose social order has taken the special form
of 'personal order.' ... A nexus enjoys 'personal order' when (a) it
is a 'society' and (b) when the genetic relatedness of its members
orders these members 'serially'.
Now after all those definitions, to come to the point in hand. A "perfect void" (in Whitehead terms, 'empty space'), is still a nexus - according to Whitehead, there still are actual occasions in an empty space. What it is not, is an enduring society (society with personal order). For Whitehead, an empty space is a spatio-temporal extensiveness with no relation of continuance in it (no "historic routes"). This means effectively that we can't measure an empty space, but it doesn't mean there aren't actual occasions inside of it - for Whitehead events pervade the extensive space itself.
In other words, time and space doesn't occupy empty space (more accurately, it is nonsensical to speak in those terms about it). But that doesn't mean there isn't anything "happening" inside it.
We may imaginatively conjecture that the first grade [i.e. empty
space] is to be identified with actual occasions for which 'presented
durations' are negligible elements among their data, negligible by
reason of negligible presentational immediacy [meaning observability].
Thus no intelligible definition of rest and motion is possible for
historic routes including them, because they correspond to no inherent
spatialization of the actual world.
... [I]t is nonsense to ask of an occasion in empty space whether it
be 'at rest' in reference to some locus... the relationship of 'rest'
does not apply to them.
In fact, for Whitehead there is a pervading electromagnetic occasions in empty space:
Thus our cosmic epoch is to be conceived primarily as a society of
electromagnetic occasions [i.e. empty space], including electronic and
protonic occasions, and only occasionally—for the sake of brevity in
statement—as a society of electrons and protons.
To conclude, Whitehead provides a systematic conception of nature that enables a different view of so-called 'empty space'. Furthermore, to answer your questions directly, according to Whitehead time is inherently related to events; but the absence of occupation in space does not mean absence of events.
[*] it should be noted that Whitehead's terms are a bit different in his other books; that's why I chose to consistently provide definitions from Process and Reality; square blocks in quotes are mine.