UFOs are Just a Sign of the Times?

I was listening to an old 'Hidden Experience' podcast about
Arthur C.Clarke where Arthur is said to have said that UFOs are just signs of the times to say humanity is growing up -
Hidden Experience Audio: Arthur C. Clarke and Multiple UFO Sightings

While I'm a big Kubrick fan, I've never paid much attention to Arthur C.Clarke's work, but I find it amusing that Mike Clelland likes to quote Clarke's "magic" quote in his books and on podcasts when talking about the UFO phenomenon.

I find it amusing that Arthur C.Clarke, Philip K.Dick and
Bill Hicks all share their birthdays on December 16th:-)
2020: A UFO Odyssey?