Time is a human measure of change in the state of objects in the Cosmos.
It is assumed by the many that time exists: that objects change due to time; that time is a linear dimension of the material universe; that time travel is possible.
In truth the idea of time is a human invention, an illusion. What we see as time is a change in the state of objects through their internal motions and interactions with other objects in the Cosmos.
Change due to time?
If I place an apple on a table, leaving it for six months, the apple will express signs of decay. Did time cause this change? No, the apple changed through the motion of microbes devouring the apple. The motion and the presence of the microbes on the apple is observable under a microscope.
What about hours, days, years?
Perhaps we think time exists because we observe hours, days and years. Our sense of the day and year is the effect of the motion of the sun and earth. On Venus or Pluto the day and the solar year will be different to that of Earth. The intervals of time is a human invention, I can easily create a new time measure by converting 24 hour time into 10 blocks, each block of time with 100 smaller units.
What about clocks?
Once the blocks of time are invented, then artificial devices are created to keep a measure of these blocks called clocks. If I destroyed all the time measuring devices in the world it makes little difference to the Cosmos, other than make it harder for humanity to organise their lives and activities.