As I've never married, I've no direct experience of having to remember wedding anniversaries but they've never featured greatly in my life anyway. My parents celebrated their silver wedding anniversary (which was the only anniversary I sent them a card or gift for) but I can't remember them even mentioning their wedding anniversary at any other time, yet alone sending cards or buying gifts for each other.
Likewise, I've not got a clue regarding the date when my lad and his wife got married, so I've never sent them an anniversary card or gift.