Michael345;
All those happenings happen at / in the same singular now,
"now" is the present, for any duration of time, hearing a sound for a second, to what is in vogue for a decade. We are considering brief short duration events.
You and your cat may be considered in the same ref. frame (house), with all your clocks synchronized. You and your cat have individual 'nows', which may be recorded as the same 'time', with no significant difference (nanosec).
You and your neighbor may be considered in the same ref. frame (time zone), with all your clocks synchronized. You and your neighbor have individual 'nows', which may be recorded as the same 'time', with no significant differences (millisec).
The communication time increases with distance. You can compensate for the delay IF you know the distance, which requires a measurement. The coordinate transformations work IF you know the velocity of the distant clock, which requires two separate measurements. Each 'now' has a different time stamp for each event for different observers, depending on their motion, which alters their 'time'. Thus 'time' is subjective.
A. Einstein, 1905 paper, par.1
[Thus with the help of certain imaginary physical experiments we have settled what is to be understood by synchronous
stationary clocks located at
different places, and have evidently obtained a definition of ``simultaneous,'' or ``synchronous,'' and of ``time.'']
The red calibration curve in the graphic represents a constant unit of time. A is a clock with an equivalent velocity as the U clock, thus at rest. The velocity profiles to either side of A will be perceived by U and A as running slower, even when synchronized.
A is the only clock that will have the same rate as the U clock when synchronized.
The astronomical distances and relative motions prevent any large scale clock synchronization
