A Google Web Search Help thread has one searcher doing research on European Central Bank (ECB) content within Ireland, but looking for content within a specific timeframe.
He was looking for a specific article from a specific paper and knew it was in Google but wanted to find it using a date restriction tool, based on knowing when the news came out.
When he used the filters together, the article was not to be found. When he removed the date filter option, the article did appear in the Google results.
So something can be wrong here:
(1) The user's query
(2) The way Google documented the date of the article in question
(3) The date filter function within Google search.
This has been reported to Google to investigate but Google has yet to respond to this matter.
Forum discussion at Google Web Search Help.