I suppose there is a bug in Organiser Feed.
Yearly appointments set as all day events which have start date before year 1970 do not show up in news feed.
I realized that today - I have a friend with a birth date on 6th January 1967 and I have all day appointment created for that. It does not show up in news feed. So I created "Test" appointment (all day event, repeated yearly) with a start date on 6/01/1967 - it did not show up in news feed either. I started to change the date to 6/01/1968, than 1969 etc. The appointment showed up in news feed when I changed its date to 6th January 1970.

[EDIT]
or maybe it is Calendar app bug itself?

regards