What is time? Another question that children may ask. Here again, mechanics offer an answer. A given time or duration can be understood as the result of a balance or ratio between opposing mechanical factors, one tending to increase it and the other tending to shorten it. In this third video of this series on mechanics we give a few examples of times that can be understood from ratios of pairs of mechanical quantities. These simple times are found everywhere, they can be used to describe the frequency of photons, the lifetime of stars like the sun, the oscillations of springs or the pinch-off and rebound of droplets. As soon as two mechanical quantities are on the same column in the table introduced in the first episode, then their ratio will produce a time scale.