Multisite Functions.php

Create your own functions.php and stick it in your /wp-content/mu-plugins/ folder.

Any *.php snippet you stick into your mu-plugins folder will be run automagically – sort of like a functions.php from your theme but more powerful – especially for a multisite.

And when you update WP, the /mu-plugins/ will not get deleted like updating a theme’s functions.php.

http://codex.wordpress.org/Must_Use_Plugins

I have 8 sites and want share my claender entrys across them akk
I am using https://wordpress.org/plugins/all-in-one-event-calendar/

my base site is http://sun103.com/events/

thanks Dewey