Precept 1. Things diffuse from a small volume into a larger one.
Precept the second. Time is diffusing. The big-bang says that time has a begining. From the begining until now is a fixed amount of of time, and also of space. From now until the end of time is a much larger volume i.e. neigh unto infinite.
1st Hypothesis. We observe time going only one direction because it is diffusing from a finite box into an infinite box. Time doesn't go backwards for the same reason gas doesn't diffuse back into the box. The probability is gas-ly small, infact if the outer box is really infinite the probability of diffusing back in is zero.
If you will allow the assumption that time is diffusing, then we can model the average path of time with the root mean square velocity, or the average speed with which a molecule of time will travel. V=(3kT/m)^(1/2) where V is the velocity, which in our case is C, the speed of light. Einstein and others have suggested that if you travel faster than the speed of light you will have traveled in time. Therefore, time travels at the speed of light or about 299792458 m/s. The symbol k is the Boltzman's constant which is equal to 1.3806504 x 10^-23 J/K and T is the temperature, or in our case the average temperature of the universe which is between 2.7280 and 2.7282 K plugging in and rearranging we see that m, the mass of time = 3kT/C^2 or 1.25726*10^-39 kg but surprizingly this unit of time does not have a "time" associated with it, so is time quantized? Is it discrete? Or is this the "rest mass of time" I don't know. However, time having a mass could account for the mysterious dark matter in the universe, if time has a mass according to DeBroglie it could have a wavelength and it might be that time itself is vibrating rather than say light or matter, perhaps it is time that gives things their duality? Oh and on a more religious note, if something is beyond time is it no longer a dichotomy? Is this what gives God his constancy? Ponder away, and I wish you luck.