Calendar woes


Any Calendar experts? Mystery here. Wife & I share our Calendars on our MBPs & iPhones (with iCloud backup). All syncs very well EXCEPT---the moment either of us clicks "All Day" (as in birthdays etc.) it disappears of 2-3 of the 4 calendars. A search (top right) shows up, but not visible on the calendars.

"All Day" is the only thing, I can tell, that messes it up. What am I doing to cause this?