Each person has his or her own frame of reference for time which begins and ends at the instant the observer (say who is tracking a photon) collapses the associated wave function and an observation is registered.

 

If 10 different observers moving at accelerated frames of reference observe the photon for the same interval as the one illustrated above they will have different times for t₀ and t_1, combining relativity with quantum mechanics.

 

However normalization of all acceleration across all possible frames of reference across the whole "Universe" for that photon will produce a single time line.

(apply limit as noofframes tends to infinity and integrate across all individual timelines).

 

This produces an absolute time frame which although difficult to conceptualize, could be said to exist.

This will be finite for the photon (which decays after 10¹⁸ years approximately) but although of a very high order of magnitude, would nevertheless be limited in it's extent.

 

Smaller frames of reference for different observers could be eventually ignored and the sum total across the lifetime of the photon be used to define absolute time.

 

Just my abstract visualization.

 

Please revert with your ideas.

 

There are an infinite number of inertial frames for which the time does not behave this way, and physics likes to deal in inertial frames.

Also, saying photons decay after 10¹⁸ years is wrong. That's a lower limit, i.e. a minimum value, for a half-life.