How do calendar apps interact?

[wpbilbo]

Please see: Question on WP.SE

I recently tried a Lumia 620 and was shocked by the built-in calendar of WP8. (I'm currently using a Symbian phone, so I've got no clue wrt. to WP8 in general.

Seeing as there are a lot of apps that try to "fix" the built in calendar I still do not quite understand how all the different calendar apps operate/interact.

Do "all" calendar apps on a phone share a common underlying calendar datastore provided by the phone? How do they sync? Should a calendar app basically be able to do the same things (wrt. to creating and modifying stuff in the calendar) as the built-in calendar?

 

[jhguth]

A lot of the calendar apps work entirely separately from the built in app, the ones that interact i think all do so by syncing with the exchange server