Its a bit more than that.

Its about scale andhaving your country shown as central to your thinking and veiw of the world.Not sure how the time and date differs thoughout the continent but Ethiopia has always had its own calander so prehaps it would be an idea to use the Ethiopian calander rather than the given european one.

http://www.ethiopic.com/calendar/ethiopic.htm

http://ethio.com/calendar.html

http://en.wikipedia.org/wiki/Ethiopian_calendar

Was thinking Cairo as Kemit is said to be the geographical center of the world but considering the Ethiopian calander is based on the one the Kamu (Imhotep - ancient egyptians) invented and itsthe birthplace of humanity it suits. The central line of longitude would run through Addis Ababarather than Grenwich.

Info about Ethiopia; http://en.wikipedia.org/wiki/Ethiopia