The Complete Aristotle (eng.)

is a measure of motion and of being moved, and it measures
the motion by determining a motion which will measure exactly the
whole motion, as the cubit does the length by determining an amount
which will measure out the whole. Further ‘to be in time’ means for
movement, that both it and its essence are measured by time (for
simultaneously it measures both the movement and its essence, and
this is what being in time means for it, that its essence should be
measured).
    Clearly then ‘to be in time’ has the same meaning for other
things also, namely, that their being should be measured by time.
‘To be in time’ is one of two things: (1) to exist when time
exists, (2) as we say of some things that they are ‘in number’. The
latter means either what is a part or mode of number-in general,
something which belongs to number-or that things have a number.
    Now, since time is number, the ‘now’ and the ‘before’ and the
like are in time, just as ‘unit’ and ‘odd’ and ‘even’ are in
number, i.e. in the sense that the one set belongs to number, the
other to time. But things are in time as they are in number. If
this is so, they are contained by time as things in place are
contained by place.
    Plainly, too, to be in time does not mean to co-exist with time,
any more than to be in motion or in place means to co-exist with
motion or place. For if ‘to be in something’ is to mean this, then
all things will be in anything, and the heaven will be in a grain;
for when the grain is, then also is the heaven. But this is a
merely incidental conjunction, whereas the other is necessarily
involved: that which is in time necessarily involves that there is
time when it is, and that which is in motion that there is motion
when it is.
    Since what is ‘in time’ is so in the same sense as what is in
number is so, a time greater than everything in time can be found.
So it is necessary that all the things in time should be contained
by time, just like other things also which are ‘in anything’, e.g.
the things ‘in place’ by place.
    A thing, then, will be affected by time, just as we are
accustomed to say that time wastes things away, and that all things
grow old through time, and that there is oblivion owing to the
lapse of time, but we do not say the same of getting to know or of
becoming young or fair. For time is by its nature the cause rather
of decay, since it is the number of change, and change removes what
is.
    Hence, plainly, things which are always are not, as such, in
time, for they are not contained time, nor is their being measured
by time. A proof of this is that none of them is affected by time,
which indicates that they are not in time.
    Since time is the measure of motion, it will be the measure of
rest too-indirectly. For all rest is in time. For it does not
follow that what is in time is moved, though what is in motion is
necessarily moved. For time is not motion, but ‘number of motion’:
and what is at rest, also, can be in the number of motion. Not
everything that is not in motion can be said to be ‘at rest’-but
only that which can be moved, though it actually is not moved, as
was said above.
    ‘To be in number’ means that there is a number of the thing, and
that its being is measured by the number in which it is. Hence if a
thing is ‘in time’ it will be measured by time. But time will
measure what is moved and what is at rest, the one qua moved, the
other qua at rest; for it will measure their motion and rest
respectively.
    Hence what is moved will not be measurable by the time simply in
so far as it has quantity, but in so far as its motion has
quantity. Thus none of the things which are neither moved nor at
rest are in time: for ‘to be in time’ is ‘to be measured by time’,
while time is the measure of motion and rest.
    Plainly, then, neither will everything that does not exist be in
time, i.e. those non-existent things that cannot exist, as the
diagonal cannot be commensurate with the side.
    Generally, if time is directly the measure of motion and
indirectly of other things, it is clear that a thing whose
existence is measured by it will have its existence in rest or
motion. Those things therefore which are subject to perishing and
becoming-generally, those which at one time exist, at another do
not-are necessarily in time: for there is a greater time which will
extend both beyond their existence and beyond the time which
measures their existence. Of things which