I haven't been following this thread very closely, so I don't know if implementation specifics of the clock have been discussed. Is it a real time clock, or does it only update on a page turn?
This is one of the issues that has been discussed in the past every time someone would request a clock feature on the iLiad or DR. A real time clock is going to be a battery drain and defeat one of the main benefits of eInk, namely that it doesn't require power to maintain a static image on the screen. It sounds like that is what is going on here, but I don't know for sure.
Based on previous discussions, the easiest way to get around that issue is to only have the clock update on a page turn. That way you're not causing any additional battery drain, however, it also means that the clock is not going to be accurate. The user will have to be aware that the clock information on the screen is outdated, unless they have recently done a page turn.