Is there a time limit to an Iron Man triathlon?

A friend of mine did a Iron man and finished in 18 hours and was not the last one, I was wondering if there was a time limit?

Did I officially do an ironman triathlon even though I went over time limit?

I did an ironman distance triathlon last weekend. All the distances were exactly the same and the same rules applied (no drafting,etc.) However, this was not an officially sanctioned ironman event. As such they let competitors go beyond the standard 17 hour time limit to finish. I finished in about 17:30.

My question is should I put a 140.6 sticker on my car? After all, I did do every bit of the 140.6 miles.