title: Schedule clockwork to run only on a specific date of the year
body: <p>I been trying schedule a job with <code>clockwork</code> to run only on day eg. February 14. But I'm not sure if is this possible because the <a href="https://github.com/tomykaira/clockwork#valid-formats" rel="nofollow">documentation formats</a> do not have this possibility.</p>
  
  <p>I know that I can do something like this:</p>
  
  <pre><code>Clockwork.every(1.day, 'valentines_day_job', if: lambda { |t| t.day == 14 &amp;&amp; t.month == 2 })
  </code></pre>
  
  <p>But I would like to avoid unnecessary verification every day.</p>
  
  <p>Any ideas?</p>
  
  <p>Thank you.</p>