Some of the foundations or tests that try to justify the relativity theory in the sense of the time variation in function of speed and gravity, it is the one relative to the backwardness/advance of clocks on airships.

On this question, I believe and suppose many manipulations in the observations and applied formulas to be able the final affirmation that "certainly the backwardness/advance of the clocks demonstrates the consistency of the relativity in the time variation", besides demonstrating an almost absolute lack of knowledge of basic physical principles.

Although when being very confuse, long and complicated of explaining the different phases of this great "confusion" (being generous when not call it manipulation), I take in mind alone the kernel of the question, which on the other hand, is vary simple.

And the kernel of the question so simple is:

The clocks are mechanical, electro-mechanics, atomic systems, etc., in which the motion that they mark always comes determined by the balances and development of the forces and elements that structure and move them.

For example, if we fit in our house a pendulum clock in such a way that it keep almost exact, and later on we take it away to the external space where there is not gravity, and there we lift the pendulum so that this way it can begins its oscillation, we will be surprised of seeing as this pendulum remains lifted and the clock doesn't move neither works.
Equal would make a sand clock, because in the outer space without gravity the sand doesn't fall.

Then we can ask ourselves: Could be that in places without gravity "TIME DOESN'T PASS"?, as erroneously a relativist could conclude.

Certainly NOT; simply the forces that move to clock don't act in this place.

In contrary sense, a spiral-spring clock due to its frictions, atmospheric pressure, etc. in the space without gravity it will "walk" speedier.

In the same way, the atomic clocks of any type; of radioactive oscillation; laser; biochemical or of any other device, they are always affected for the gravitational fields, temperatures, etc.

In this case, far from the gravitational fields the atomic clocks advance a little speedier because the gravitation is a force that exercises certain "pressure" on atoms, decreasing its oscillation and this way its rhythm of measuring time.

But we could also make a clock of nuclear fission in which the gravity increase the atomic disintegration giving us an advance in the clocks.

As we see, while the pendulum clocks (and others) advance speedier in the gravitational fields, the atomic clocks (and other) delay in these fields.

And the question is logical and necessary:

Of course that any relativist will make anything to demonstrate its theory; although this intent is ridiculous and stupid for incongruous and unhappy.

For the speed of light to be constant, it is necessary that space and time be stationary, because if the different frames of reference also have different times and different local space, then it is not possible to keep the speed of light constant between a frame A and frame B.

Dear relativists, sorry to be a little aggressive, but sometimes it is necessary to be a little hard if we want to be clear and comprehensible.

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.

Ferman.