While "ordinary" questions have their birth time readily visible above the original poster name, it seems like the only way to find out when a CW question has been asked is to view its revision history page. Is this intended?
But, to be honest, the explanation of this choice given there does not seem very satisfactory to me. The answer there seem to suggest, that since community wiki post is supposed to be common work by several users, the date of creation does no matter.
More than with the answers I tend to agree with this comment:
The question is tagged "by design" without explanation, what are design reasons. IMHO, creation date may be more important than the name of the most contributor, since it's agreed, that the author is a Community. -- Michael Freidgeim
But since the question was inactive for a long time (all answers are from 2009, and it was marked as status-bydesign around the same time, the above comment is from 2013), I find it rather unlikely that some additional explanation will be given there.