Iphone 4s calendar not showing anniversaries

[Droidconvert]

I was surprised when I went in my calendar that it is not picking up anniversaries from my contact information. It picks up birthdays but not anniversaries. Is there a trick to make it work? I asked Siri what day was my anniversary and she could not answer the question. My anniversary is showing in my contacts and also my wife's contact. Any help would be appreciated. I am brand new to Iphone.

Thanks in advance!!