The Complete Aristotle (eng.)

body and
the number of its locomotion. For the number of the locomotion is
time, while the ‘now’ corresponds to the moving body, and is like
the unit of number.
    Time, then, also is both made continuous by the ‘now’ and
divided at it. For here too there is a correspondence with the
locomotion and the moving body. For the motion or locomotion is
made one by the thing which is moved, because it is one-not because
it is one in its own nature (for there might be pauses in the
movement of such a thing)-but because it is one in definition: for
this determines the movement as ‘before’ and ‘after’. Here, too
there is a correspondence with the point; for the point also both
connects and terminates the length-it is the beginning of one and
the end of another. But when you take it in this way, using the one
point as two, a pause is necessary, if the same point is to be the
beginning and the end. The ‘now’ on the other hand, since the body
carried is moving, is always different.
    Hence time is not number in the sense in which there is ‘number’
of the same point because it is beginning and end, but rather as
the extremities of a line form a number, and not as the parts of
the line do so, both for the reason given (for we can use the
middle point as two, so that on that analogy time might stand
still), and further because obviously the ‘now’ is no part of time
nor the section any part of the movement, any more than the points
are parts of the line-for it is two lines that are parts of one
line.
    In so far then as the ‘now’ is a boundary, it is not time, but
an attribute of it; in so far as it numbers, it is number; for
boundaries belong only to that which they bound, but number (e.g.
ten) is the number of these horses, and belongs also elsewhere.
    It is clear, then, that time is ‘number of movement in respect
of the before and after’, and is continuous since it is an
attribute of what is continuous.
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12
    The smallest number, in the strict sense of the word ‘number’,
is two. But of number as concrete, sometimes there is a minimum,
sometimes not: e.g. of a ‘line’, the smallest in respect of
multiplicity is two (or, if you like, one), but in respect of size
there is no minimum; for every line is divided ad infinitum. Hence
it is so with time. In respect of number the minimum is one (or
two); in point of extent there is no minimum.
    It is clear, too, that time is not described as fast or slow,
but as many or few and as long or short. For as continuous it is
long or short and as a number many or few, but it is not fast or
slow-any more than any number with which we number is fast or
slow.
    Further, there is the same time everywhere at once, but not the
same time before and after, for while the present change is one,
the change which has happened and that which will happen are
different. Time is not number with which we count, but the number
of things which are counted, and this according as it occurs before
or after is always different, for the ‘nows’ are different. And the
number of a hundred horses and a hundred men is the same, but the
things numbered are different-the horses from the men. Further, as
a movement can be one and the same again and again, so too can
time, e.g. a year or a spring or an autumn.
    Not only do we measure the movement by the time, but also the
time by the movement, because they define each other. The time
marks the movement, since it is its number, and the movement the
time. We describe the time as much or little, measuring it by the
movement, just as we know the number by what is numbered, e.g. the
number of the horses by one horse as the unit. For we know how many
horses there are by the use of the number; and again by using the
one horse as unit we know the number of the horses itself. So it is
with the time and the movement; for we measure the movement by the
time and vice versa. It is natural that this should happen; for the
movement goes with the distance and the time with the movement,
because they are quanta and continuous and divisible. The movement
has these attributes because the distance is of this nature, and
the time has them because of the movement. And we measure both the
distance by the movement and the movement by the distance; for we
say that the road is long, if the journey is long, and that this is
long, if the road is long-the time, too, if the movement, and the
movement, if the time.
    Time