title: Azure WebJob not accepting a valid(?) CRON expression
body: <p>I used <a href="http://crontab.guru/" rel="noreferrer">crontab.guru</a> to create a very simple CRON expression with the desired behavior to execute every day at 3:15 (AM) and this is the result: <code>15 3 * * *</code></p>
  
  <p><a href="https://i.stack.imgur.com/8c3Vj.png" rel="noreferrer"><img src="https://i.stack.imgur.com/8c3Vj.png" alt="Crontab.guru"></a></p>
  
  <p>Unfortunately for me, in <a href="https://portal.azure.com" rel="noreferrer">Azure Portal</a> this does not work, but if I add a leading <code>0</code> to my expression as such, <code>0 15 3 * * *</code>, Azure will accept it, while <code>crontab.guru</code> will tell me it is wrong. The specification according to <code>crontab.guru</code> is: <em>minute hour date month weekday</em>.</p>
  
  <p><a href="https://i.stack.imgur.com/pUTzn.png" rel="noreferrer"><img src="https://i.stack.imgur.com/pUTzn.png" alt="Azure does not accept my CRON expression"></a></p>
  
  <p><a href="https://i.stack.imgur.com/QbFcE.png" rel="noreferrer"><img src="https://i.stack.imgur.com/QbFcE.png" alt="Azure accepts the expression with a leading zero"></a></p>
  
  <p>The questions..</p>
  
  <ul>
  <li>From where comes the discrepancy? </li>
  <li>Is it Microsoft that in their traditional ways have a proprietary
  implementation with a leading zero? </li>
  <li>If the standard is <em>minute hour date month weekday</em>, what does the
  leading zero describe?</li>
  </ul>