To my way of thinking, the only two people who might want to keep track of that exact date are the bride and groom. Or groom and groom. Or bride and bride.
Apart from them, I figure everyone else is off the hook.
I do remember some of my friends' anniversaries, but generally that's only true if I've attended the wedding. On the hand, I've been in two weddings, and with apologies to my sister and my friend Susan, I can't tell you the date of either one. I do recall that they were two weeks apart. In August. And I was was damn sweaty for both of them.
I don't think I've ever sent an anniversary card to friends, but if were to see friends, and it also happened to be the date in question, I'd congratulate them. I'm not a complete ass, after all.
"Big Anniversaries," the 10's the 25's, 50's are usually accompanied by a party that makes remembering the precise date of the wedding somewhat beside the point.
Today would have been my parents' forty-third anniversary. In reality, they only had thirty-eight anniversaries, but in my head I keep tallying. It was always easy for me to keep track of how long they were married--I just added one to my age. That system no long really works, since 38 stays fixed, while I keep getting older.
I have no real point to make here. This just happens to be on my mind today.