title: Converting a year from 4 digit to 2 digit and back again in C#
body: <p>My credit card processor requires I send a two-digit year from the credit card expiration date. Here is how I am currently processing:</p>
  
  <ol>
  <li>I put a <code>DropDownList</code> of the 4-digit year on the page.</li>
  <li>I validate the expiration date in a <code>DateTime</code> field to be sure that the expiration date being passed to the CC processor isn't expired.</li>
  <li>I send a two-digit year to the CC processor (as required). I do this via a substring of the value from the year DDL.</li>
  </ol>
  
  <p>Is there a method out there to convert a four-digit year to a two-digit year. I am not seeing anything on the <code>DateTime</code> object. Or should I just keep processing it as I am?</p>