This post just uses the path metadata--it's a setting in pelicanconf.py to extract metadata from the file path and name.
This is handy if you just want to write a minimal amount of text, and have Pelican figure out the metadata.
A gotcha
If the file is named something like "2014/12/26_my-post.md", and you edit the file on December 27th, the file system modification date will be used, so it won't appear at /2014/12/26/my-post/, but rather at /2014/12/27/my-post/
On a dev server, this will appear at
http://localhost:8000/2014/12/27/path-metadata-messing-around/