Nonautonomous differential equations on finite-time intervals play
an increasingly important role in applications that incorporate
time-varying vector fields, e.g. observed or forecasted velocity
fields in meteorology or oceanography which are known only for
times $t$ from a compact interval. While classical dynamical
systems methods often study the behaviour of solutions as $t \to
\pm\infty$, the dynamic partition (originally called the EPH
partition) aims at describing and classifying the finite-time
behaviour. We discuss fundamental properties of the dynamic
partition and show that it locally approximates the nonlinear
behaviour. We also provide an algorithm for practical computations
with dynamic partitions and apply it to a nonlinear 3-dimensional
example.