Lately Google seems to have put forth most of the little niceties that turn forgetful, or otherwise inept, people into functional members of society. Late Wednesday Facebook rolled out one of its own features that falls within that category. Now those who are lucky enough to be in a relationship can plug in when their love affair began. Facebook will then send both of those users a reminder (in the form of an event) when it's coming up.
Right now the feature has the same privacy level as a relationship, so if your friends can see it, they can also see the date. Although they will not be alerted to it the same way they are for something like a birthday--something Facebook says could eventually change.
Maybe this is the first step in Facebook creating something similar to its now-removed friends timeline feature, but for relationships, so that users will be able to get a chronological view of every relationship other users have had. Though in truth, this is likely just another way to make it easier to sell advertising for things like chocolates, flowers, jewelry and "sorry I missed our anniversary" cards.