Mr. Greer, feed this to Fido if you think it looks like frontrunning your replies. Anonymous posting should take a bit of the "your blog" (which of course, it is) off from the problem, that is possibly scaring away a lot of people of replying to questions.

Mr. Greer told about the need of integration. I think that the loss caused by the collapse of industrial civilization would need to be immense to clear away the seven days week. If that happened, it is likely that the knowledge about the existence of the planets would be lost too.

My take on it is that nine day weeks might have specialized applications in the far-future; but since these will not be collective, shared by the whole world, they would be necessarily weak. It is possible that these two planets would use their own cycles, separated from the normal week, at best. I would bet on them fading into irrelevance instead.