title: Defining a table with sqlalchemy with a mysql unix timestamp
body: <p>Background, there are several ways to store dates in MySQ.</p>
  
  <ol>
  <li>As a string e.g. "09/09/2009".</li>
  <li>As integer using the function UNIX_TIMESTAMP() this is supposedly the traditional unix time representation (you know seconds since the epoch plus/minus leap seconds).</li>
  <li>As a MySQL TIMESTAMP, a mysql specific data type not the same than unix timestamps.</li>
  <li><p>As a MySQL Date field, another mysql specific data type.</p>
  
  <p>It's very important not to confuse case 2 with case 3 (or case 4).
  I have an existing table with an integer date field (case 2) how can I define it in sqlalchemy in a way I don't have to access mysql's "FROM_UNIXTIME" function?</p>
  
  <p>For the record, just using sqlalchemy.types.DateTime and hoping it does the right thing when it detects an integer column doesn't work, it works for timestamp fields and date fields.</p></li>
  </ol>