I looked at the Wiley-Interscience web site. They're bragging about a pilot project with Google and CrossRef to reissue old articles online; maybe this is the problem.
Next day: Quick and helpful response from Google Scholar:
Unfortunately, yes, it looks like Wiley's abstracts occasionally have online dates instead of publication dates.
Thanks for bringing this to our attention. We'll contact Wiley but it will take some time for this to get resolved. In the meantime, a workaround when searching for recent articles is to add -site:wiley.com to your query, like so:
The Google Scholar Team