I have been collecting 1/64 NASCAR diecast since 12/26/92. It is my primary hobby and how I discovered the sport.
I don't know when I started collecting street cars-possibly as far back as 1985. I also have my brother's collection. I pretty much stopped collecting street cars in 2000, but I have slowly gotten back into it over the past few years. It's a lot cheaper and easier to store than full size cars.
My primary collection will always be NASCAR, though.
I take Christmas 1985 as the date I started collecting. I am not sure if it's correct but that's the date I go by.