coordinates are fixed?

is the relationship between the physical and the mathematical.
The interval is fixed by these two components:

the physical fixed-quanta matter
changing from one fixed spatial location to another fixed spatial location.

physical space = mathematical fixed point coordination

Time intervals are assigned to a specific, mathematical, perfectly repetitive numeric values. However, perfect intervals are continually subject to any possible changes that actually, physically alters this perfect mathematical fixed-interval. These physical intervals are based upon the physical reality of the specific repetitive physical cycle being monitored and utilized as the measuring device; a clock.

Physically, quanta/mass changes fixed-point coordinations. This displacement of quanta can be observed and mathematically given an interval. This precise mathematical interval, however, will always be subject to the physical reality of the measuring device that calibrates the interval, as well as to the variations of the physical object itself.

Einstein stated that "equal time cannot be established by points that are not connected by a light signal."

A confusion arises when considering the measurement of time. Clocks and the measurement of the passage of time can only ever be as accurate as long as the physical nature of the timing mechanism remaining consistent. The physical timing can be altered by conditions, but this will only change the timing of your device and that is quite different than a conclusion that it is time that has been changed. This "consistency" even differs from one ceasium clock to another. Although extremely precise, they are not totally consistent. Time passage should not be confused with the measurement of time.

Like the tree that falls in the forest - it is not the perception of a phenomena that determines whether or not the tree actually topples, nor if sound was made from the topple. We have been mis-led to conclude that if we can use a mathematical - conceptual technique to show that we can measure time differently, that in fact time is not absolute. This conclusion regarding time variances is my fundamental arena of contention. With a different comprehension of time and its intrinsic properties, an entirely different perception is possible: universal time. That is, as one second passes at your location, that same second passes everywhere simulaneously. One cannot alter this fact, by either being close to a large mass or travelling faster than light. Aging is a factor of universal time, not velocity, nor mass proximitry.

Einstein states that "time is what we measure with a clock and distance with a measuring rod".

His is a somewhat ambiguous statement, if not even, completely mis-leading. It is subtle in its inference, in that somehow if we should not measure the same time for a singular event from two different locations, that the event does not, nor cannot be associated with only one particular time frame.

The ability to measure time accurately is dependent upon the device used to measure it. If something was measured as to the length of its duration by two different techniques or devices and a difference is found in duration times, then it is the device or technique that has had its ability to accurately measure the duration and this comparison of measurements should not be concluded that it is time itself that has been altered.

Whatever device such as a clock, or celestial event, such as the passing of one body around another, is used to determine any specific interval of time, requires the physical monitoring of some naturally occurring phenomenon.

The measurement of time can be effected by an alteration to the occurrence of the phenomenon being monitored.

The fact that there is a difference in our measurements under such conditions as flying one clock around the Earth in a direction against the Earth's rotation, as compared with a stationary clock, points more to the possibility that the a physical change had occurred in the rate at which the phenomenon occurred; and not any evidence to support the claim that time can be altered. That is to say, the cesium clock in the trip around the Earth has had its change in the measurement of time because of the physical reality of the change upon the cesium atoms. It is the cesium atoms themselves that are physically effected by the conditions imposed upon them; not time that has been effected, only the measurement of time.

The relativity theories of Einstein conclude that "time is not absolute, it is relative".

His conclusion was brought about through the use of the mathematics involved between only two different observer positions.

This concept of a relative time as expressed by Einstein is true only if no distinction is made between an event and the light horizon generated from that event. This distinction is however, very important to make. If you lump them together, the event - and the light horizon from the event, then your mathematics and mis-understanding of time will be effected by this non-differentiation.

The light horizon/event generated from an event is not the same as the event.

The light horizon from an event occurs after the event in an absolute sense with respect to time.

The light horizon from an event travels away from that event location only after the event has already taken place.

Events happen in an absolute sequence.

Event horizons from events will be seen in a sequence not equal to the absolute sequence of events.

Event horizon sequence depends upon the location of the observer.

Event horizon sequence will be different at every location from every other location as well as unique at each location.

Absolute event sequence occurs whether or not there is a measurement of it or an understanding of it.

Once an event has occurred, you cannot travel from any place else in the universe, no matter at what theoretical speed to ever be able to arrive at that location and see the event.

Once an event has occurred, you would theoretically be able to see this event horizon from this event forever; if you were at the proper distance from the event at a corresponding time interval from the event.