title: Excel - How to count unique days in a list a duplicated days
body: <p>Having a list of days suchs as:</p>
  
  <pre><code>01-giu-16
  01-giu-16
  01-giu-16
  31-mag-16
  31-mag-16
  31-mag-16
  31-mag-16
  30-mag-16
  </code></pre>
  
  <p>I was looking for an excel formula that helps me count the number of unique days in the list (in this example 3)</p>
  
  <p>Moreover I need the count only for the dates which have a specific ID in the next column (for example 1565)</p>