I would like to point out that setting a particular "contact time" for while the earth's rotation is stopped is futile prior to the pole shift for HF radio. Propagation characteristics are a function of the sun's position relative to the two sites attempting communication. We will have no idea what that will be during the period of no rotation. After earth resumes normal rotation, and each location is able to establish the exact times of sunrise and sunset, it will then be possible to utilize propagation charts to determine the optimum time windows to other sites. So instead of establishing a set time prior to the pole shift, we need to do two things.
Note: These comments apply to HF propagation only. VHF/UHF communications over a line-of-sight path are not affected in the same way and should be useful 24 hours a day except possibly during the 12th's passage due to magnetic interference.