Danny Sullivan of Google said by Friday the bug with using the custom date range in Google Search. There are numerous complaints about it not filtering the results to the date range you selected. Danny said on Twitter "yes, there's a bug we expect to be fixed by Friday."
Here is what the feature looks like, you can access it after doing a search and clicking on "tools" and then "any time" and then "custom range."
Until Google fixes it, he recommends you use the before and after search commands.
Forum discussion at Twitter.
