JQL Search not returning the correct results

When performing an advanced search filtering for the "create" field, it doesn't return the correct number of issues. For example, if we create an issue at '2011-04-04 12:02' and perform a search with the filter created <= 2011-04-04, the issue create at 12:02 is not returned. I believe the system, in this case, performs a search like created <= '2011-04-04 00:00'.