title: SQL Date Formats - Counting days since date field
body: <p>I am working with some dates in SQL and wanted wanted help to manipulate it. I have a list of birthdates and wanted to do things such as...</p>
  <ol>
  <li>Cast the date in a select statement (e.g. if a person is born before 2000 is 'pre-2000' and those born after 2000 are 'post-2000'.</li>
  <li>Filter the selections so only those born after 2000 are included in the statement.</li>
  <li>Calculate the number of days in current time since the person's date of birth.</li>
  <li>Reformat the date with letters inbetween e.g. &quot;1990y 11m 01d&quot;</li>
  </ol>
  <p>The format of the field is DATE.</p>
  <p>How can I do so?</p>
  <p>Sample date is &quot;1990-11-01&quot;. I am using Amazon Athena to query the data.</p>