We understand that the Cosmos or Universe have space and time as basic structural elements.
In order to measure these elements, we choose standard units that allow us to carry them out.
We already know that for the space we have adopted the standard unit of the metre (platinum bar kept in the Museum of Weights and Measures in Paris .....)
But and for time, which element or standard system have we chosen?
Well, a quite perfect one, since it does not depend on us but is a system or physical and natural element already created by cosmic events:
I am referring to the time of orbital rotation of the earth on the sun, which we use as a multiple unit of time, the year.
Well, if we analyze this planetary orbit of ours, already accepted as a unit of time, we will see many interesting peculiarities of it.

1.- The main peculiarity is that this natural or cosmic orbit, which we use as a unit of time (the year), is quite stable and that is why we choose it.
Well, we will call this orbital clock, established as a unit of time, the Master Clock, and by it we will guide ourselves to build any other clock.

2.-By choosing this unit of time and being quite stable, we take it and accept it as a "unit of measurement of real and true time", that is, all clocks will be aligned and timed with respect to this unit, and if any clock built "in the image" of the Master Clock varies or is disconnected by the influence of some harmful or distorting element, we will understand that it is the replica or mechanical device (or of any other type, chemical, sand, atomic, pendulum, etc.) it is the one that fails, but that the real and true time remains in the chosen time unit or Master Clock.

3.- This planetary orbit around the sun is similar (but larger) to how we have built most of the time-measuring clocks (a flat circle with markings on its outer circumference).
If we now draw an earth orbit around the sun, we could put it (as in the drawing) the marking along this orbital circumference.

4.- These properties and peculiarities of the Master Clock undo many of the relativistic claims of time dilation according to place, speed, etc.
Real time is always that measured by the Master Clock, which does not suffer the harmful effects of the elements that affect other secondary clocks such as temperature, pressure, gravity, acceleration, etc., depending on how these approximation devices are built.
Thus, all the clocks that we use to measure time are imperfect devices that will be affected by many external elements that will influence their internal function, and that their variable operation does not influence the cadence and rhythm of true real time, measured with greater precision by the Master Clock.
To understand this I ask a simple question.
If we take a pendulum or sand clocks to a high mountain, it will mark the time much slower; then:
Does this mean that time is very slow there?
Well no, these clocks simply vary with altitude.

5.- Another quality of this Master Clock is that because it consists of a planetary orbit around the sun, it is composed of an environment of space, thus composing a frame of reference of space and time at the same time, with which we can analyze many physical (and relativistic) aspects of this frame of reference.
For example, with the master clock and the interior space that delimits it, we can measure the speed of light that passes through it and for which, the time (measured by this clock) is common to the entire system, we can even check that for a rocket with a speed close to that of light, time is universal and stationary without any kind of dilation, and that this space does not shrink for the ship at this speed.

Thank you