The punchcard might conceivably be useful for attempting to coordinate with the developers at the time when they're most active. Other than that, it does sort of feel like they just had a bunch of data lying around that they felt really needed to be shoved into a graph.
It actually plots the local time, i.e. a commit at 3am PDT and another at 3am EST would contribute to the same circle on the plot. (I did a clone of the old GitHub graphs a while back.) So it isn't really useful for knowing when to contact faraway developers. On the other hand, it is fun to see how many committers are regular night owls.
