Not a dev, just a user, but you may wish to have a look at this section of the web-site where it explains the current searching options and the “Go to Anything” search (which includes searching for tags and notebook names).
That being said, the search capabilities are being overhauled at the moment as a result of a Google Summer of Code (GSoC) Project. The progress can be found in this forum category.
In the desktop application, press Ctrl+G or Cmd+G and type a note title or part of its content to jump to it. Or type # followed by a tag name, or @ followed by a notebook name.
There's no mention of searching by date because there is no searching by date that I am aware of. I guess that's why searching was seen as something to be picked as a GSoC project.
EDIT: Extract from the Project Goals
Implement the Okapi BM25 ranking function.
Implement additional keywords to refine the search.
This is a relatively new plug-in, which can realize embedded search and sorting of search results. You can even directly display the contents of the searched notes. You can pay attention to it.