Animals have adapted behavioral responses corresponding with light and temperature events to respond to and anticipate basic bioenergetics due of heterotrophy. Authentic Biochemistry . 28/10/2020

Since space and time are never the same twice and indeed are relatively uncertain, not even the day/night chronicity is a true cycle. It is a pattern or a familiar sequence of events and nothing more. No two moments are identical and so our internal circadian clock tracks these patterns but the means by which this detection operates at the cellular and molecular level, as well as the event itself involving the revolving celestial bodies in constant flux so in time, the pattern becomes less uniform while the ideal presents as fixed and familiar so to be displayed intentionally and subsequently neurologically as apparent classical experiential phenomena.

Feedback loops compose the ‘molecular clock’ which is governed by a cascading transcription and translational   regulatory mechanisms that are sufficient to maintain circadian rhythms.

Journal of Molecular Endocrinology (2019) 63, R93–R102