I looked it up. It was released on 8 Aug 1980.

I was just about to start 8th grade. And that's RIGHT about the same time my Dad took me to see "The Final Countdown" and "Raise The Titanic". I did not see Xanadu till it came on Cable a year or so later. Then and NOW, I love Olivia skating down the sidewalk in that white skirt, along the beach front! Man! She was such a beautiful lady!