 <p>Well, that's sorting them in descending order. You could sort them in <em>ascending</em> order like this:</p> <pre><code>customers.Sort((x, y) =&gt; x.DateOfBirth.CompareTo(y.DateOfBirth)); </code></pre> <p>If that's not what you were worried about, please specify what the problem is. Saying you don't get the expected result isn't very precise...</p>