Rate of time progression We know time can dilate, but what about the base "rate" of how "fast" time progresses?
Is it even possible to conceptually pinpoint what time would be progressing relative to?
Some relevant points might be why we can't seem to go backwards in time without tricks like traveling really fast, which isn't FUNDAMENTALLY having time travel backwards. And if time travels forwards, at what "rate", if that is a valid question at all.
Let me give a little bit of background of where I'm coming from with this question.

It started when I was thinking about a universal standardized unit of distance, which would be based on the most universal and fixed thing we know of: light. light travels at X meters per second. If we have a standard chunk of time, we could take the distance the light travels during that time, divide it up by a round number like 10^10, and we would get a "light angstrom"
Now I thought I could do this for time, but I realized I just standardized my "light angstrom" unit of length relative to the unit of time we call seconds. So that got me thinking, "Time is like an independent variable... or is it?" 
If we were to try to standardize a unit of time with another alien species based on something fundamental to the laws of physics rather than an arbitrary division of an arbitrary planet rotating an arbitrary sun, do we have anything fundamental and universal reference point to base it on?
Thanks for hearing my story. I hope it illustrates the question clearly, and where I'm coming from. It's a bit hard to communicate the question succinctly and frame it in the a succinct, abstract form.
 A: 
If we were to try to standardize a unit of time with another alien species based on something fundamental to the laws of physics rather than an arbitrary division of an arbitrary planet rotating an arbitrary sun, do we have anything fundamental and universal reference point to base it on?

Yes. For example, the second is currently defined according to an atomic standard, which aliens would be able to reproduce.
There is also the question of whether all clocks behave consistently with one another, to within their precision, if they're in the same place at rest relative to one another. Relativity requires that they do. If an experiment shows a violation of this principle, then it would be a problem for relativity. Experiments of this type are called clock comparison experiments.
An early experiment that can be interpreted as a clock comparison experiment was the 1960 Hughes-Drever experiment, http://en.wikipedia.org/wiki/Hughes-Drever_experiment . Section 5.2 of this review article http://relativity.livingreviews.org/Articles/lrr-2005-5/ describes some more recent results. Some good, recent examples:
Matsakis, Astronomy and Astrophysics 326 (1997) 924, http://adsabs.harvard.edu/full/1997A%26A...326..924M
Guena, Improved tests of Local Position Invariance using 87Rb and 133Cs fountains, http://arxiv.org/abs/1205.4235
As suggested by the title of the second paper, these can also be taken as tests of whether the laws of physics vary from one location to another.
