Birds living by the shoreline perceive time by the shifting of the tide. In nearly all other animals the perception of time depends mostly on the circadian rhythm; the changing between light and dark.
Now that an orange glow of greenhouses fills the nightly air, my sleep cycle is deeply disturbed. In an attempt to restore the cyclical phases in my life, I try to follow the rhythm of the tide. By going to a nearby coast at every ebb and flood, I try to understand the constant fluctuation of the weather, the sea and all creatures surrounding it.
As the tidal waves wash the hours away, my understanding of light and dark are slowly recovering.
* Clepsydra is another word for water-clock, an ancient method of keeping track of time.