title: Storing a calendar day in sqlite database
body: <p>I need to store items with a calendar date (just the day, no time) in a sqlite database.  What's the best way to represent the date in the column?  Julian days and unix seconds come to mind as reasonable alternatives.  If I go with a unit other than days at what clock time should it be?</p>
  
  <p>Update: I am aware of ISO8601 and actually used it to store the date as a string in YYYY-MM-DD format for the prototype.  But for various arithmetic I have to convert it to some number internally, so I'd prefer to store a number and just convert to string for display.  What units should this number be in, with what origin, and if the units is more precise than days what time of day should be used?</p>