So because the mail app from Apple is far from perfect and never showed me the date and time of calendar invites from MS Exchange environments (after the Yosemite update) I was adviced to re-add the exchange account in Preferences -> Internet Accounts.
After doing that, the calendar app just won't show the exchange account anymore. It's right there in the settings, but not in the panel:
Can anyone tell me how I get my exchange calendar back to the calendar app?
Thanks in advance for any help.
PS.: the bug in mail (no date&time for cal invites) wasn't fixed by this btw.
Best Answer
I feel stupid for answering this myself because the "fix" is idiotic.
I hope another answer gets two upvotes if they help someone so they're assigned the bounty I put out on this question. Thanks for the answers!