Share calendar outside domain

Okay so I successfully set up my mail with Google for my domain. Now the problem is the calendar.

I want to use the same calendar for both my domain and my personal account.

For some reason, I cannot grant all access outside my domain to my primary calendar. If I share my non-primary calendar, then the events don't show up on my personalized start page (seems to only use primary calendar...)

Is there anything I can do?