I use PluXml[1] for a while on my personal blog en other sites I've created. The contents is stored in XML files. To be fast, the post creation date and tags are stored directly in the filename. This hence benefits from native OS file search.
Oh wow I had never thought of this. My favorite method was to duplicate a daily task list in Evernote every morning, and resetting all the inputs. I'm going to automate that process now. You might have just solved the storage model part of my design. Thanks for taking the time to share!
[1] https://github.com/pluxml/PluXml