Mr. H.B. found this article at our friends from phys.org, and it's a stunner if one stops to think about it:

Experiment shows that arrow of time is a relative concept, not an absolute one

What is interesting - and, I would aver, pregnant with implications - is that while the overall arrow of vector of time in the macro-verse (if one may so speak), remains fixed by the second law of thermodynamics, there can be localized reversals of that vector of time due to the phenomenon of particle correlation:

The idea of entangled particles has been in the news a lot lately as researchers around the world attempt to use it for various purposes—but there is another lesser-known property of particles that is similar in nature, but slightly different. It is when particles become correlated, which means they become linked in ways that do not happen in the larger world. Like entanglement, correlated particles share information, though it is not as strong of a bond. In this new experiment, the researchers used this property to change the direction of the arrow of time. The experiment consisted of changing the temperature of the nuclei in two of the atoms that exist in a molecule of trichloromethane—hydrogen and carbon—such that it was higher for the hydrogen nucleus than for the carbon nucleus, and then watching which way the heat flowed. The group found that when the nuclei of the two atoms were uncorrelated, heat flowed as expected, from the hotter hydrogen nucleus to the colder carbon nucleus. But when the two were correlated, the opposite occurred—heat flowed backward relative to what is normally observed. The hot nucleus grew hotter while the cold nucleus grew colder. This observation did not violate the second law of thermodynamics, the group explains, because the second law assumes there are no correlations between particles.

(Italicized emphasis added.)