title: Better to use zero-date '0000-00-00 00:00:00' or NULL in MySQL?
body: <p>Is it a better practice to use default date '0000-00-00 00:00:00' or <code>NULL</code> on a MySQL database?</p>
  
  <p>I have read best to use default date '0000-00-00 00:00:00' for the reason of calculations</p>
  
  <p><em>i.e.</em> <code>&gt;</code>than a date less than a date.</p>
  
  <p>Also on time best to store <code>00:00</code> or <code>NULL</code> if time is not known.</p>