Your iOS device wants your to forget your spouse
Maybe it wants you ALLLLLLLL to itself! Maybe it's not Siri we are talking to, but Loki instead. Either way, forgetting your anniversary because it's not on your iOS calendar (Apple and Fantastical, I'm looking at you) is sure to get you into trouble.
Busy Cal, Fantastical, Busy Contacts, even Contacts has a space for anniversaries. Works on the iMac. iOS devices? Nah! No pesky spouse stuff here! LOL!
So guys, I'm not sure I just gave you a loophole to forget your anniversary, but you're not off the hook for forgetting another family member's BIG anniversary. *cough* so I've heard. You know. From someone.
Any resolution to this other than creating a Dates To Remember calendar and painstakingly going through your entire address book to look for anniversaries and enter them, then share that? Seems like such an oversight.
This certainly set me on the right track, and YES! Exporting and importing was just the ticket. I did go about it slightly more different. I also have Busy Cal and it was super easy to export the Anniversary calendar. Importing was a breeze.
I see that the new version of Busy Cal for iOS has the ability to use Anniversaries. I can't confirm for others since I don't own the iOS version.