3-4 years ago if I remember correctly. It all started with one of those bracelet you were supposed to wrap twice around your wrist. Had to check if I could get it around my neck as well because science and curiosity and stuff. Turns out it worked pretty well xP
Used to have a small silver raven as a tag on it before too, but I've since put that back to it's real purpose of being and actual necklace
(http://imagizer.imageshack.us/v2/800x600q90/600/kuwh.jpg)
In short, I've been wearing collars for longer than I've been a furry xD