If the TIME was not defined and quantified, nothing could have orderly done by Us on Earth. Length and Duration of Time differ from place to place. So, it's almost impossible to measure time.
All the celestial objects are ‘energy units’ in the universe (which itself is energy in the form of Akash) and are in “motion” always. They “rotate” (Atma Pradakshina or Bhramana) and also “revolve” (Pradakshina or Paribhramana) around a higher energy unit as its ‘centre’.
Earth, where we ALL live on also is an energy unit in Universe. It rotates (spins) and revolves around the SUN. All other grahas in Solar System also do the same. (Moon revolves TIME concept through observation of MOTION around the Earth).
The spinning or rotation of Earth ‘generates’ the feeling of something progressively happening to those who are on it. We, therefore, witness the “change” in what we see around us from morning through next morning. This has caused the concept of TIME in human minds in ancient times only.
Thus, the time between two sun rises in sequence, is taken as ‘one day’. As this period consists ‘sun appearing period’ (aha) and ‘sun not appearing period’ (ratra), the DAY is also came to be known as “ahoratra”.
“Time” must be measured/quantified to understand and experience it.
