When it appears in calendar it tells me not only whose anniversary it its but which anniversary.
Does it depend on the version of Calendar? I have Version 11.0 (2245.5.3) and entered our anniversary date, which appears on the wedding date and repeats, although it does not say which anniversary. The result was different when I entered my daughter's anniversary date in her Contact card. It is noted in the card, but it does not appear in Calendar anywhere.