As opposed to the northern/southern hemisphere that has:
- a clear reference point (equators)
- traditionally we don’t model a rotation north/south
Western/eastern hemisphere
- doesn’t have a clear reference (Greenwich?)
- traditionally we model rotation on the north/south axis so western/eastern would depend from the time


To add to your comment: The Middle East is called „Naher Osten“ (close east) in German. „Der Osten“ (the east) on the other hand refers to the ex-GDR States.