Time hasn’t always been kept by mechanical clocks and wristwatches. There was a time before that, when it was measured against the gliding of the Sun across the horizon or the passage of sand through an hourglass.
An ancient Roman time-keeping device told time through the flow of water.
The clepsydra a.k.a. a water clock consisted of a cylinder into which water dripped from a reservoir. These devices would time the speeches of orators. As late as the 16th century, Galileo Galilei would measure the rate of falling bodies with a model that was filled with mercury.
Today, the concept of a clepsydra has a different resonance.
The waterfall at the Osaka train station is, in essence, an aquatic timepiece, which displays the hours as digital readouts. The sluicing liquid can also shift-shape and show floral motifs and texts.