title: Iterate over days, starting from x date through an end date
body: <p>I need to start from, for example, January 1 2013, and "do some things" for each date, resulting in a JSON file for each date.</p>
  
  <p>I have the "do some things" part worked out for a single date, but I'm having a hard time starting at a date and looping through to another end date.</p>