 <p>Actually you can use <code>ToString()</code> , but it depends on your dll version.</p> <p>the correct approach is to use the <code>Month</code> property of the <code>Datetime</code></p> <p>Comparing two datetimes by month</p> <pre><code>Datetime1.Month == Datetime2.Month </code></pre> <p>or if your Datetime is a nullable</p> <pre><code>Datetime1.Value.Month == Datetime2.Value.Month </code></pre> <p>so a correct linq query would be for example</p> <pre><code>(from p in Source where p.DT.Value.Month == RequestedDatetime.Value.Month select p) </code></pre> <p>Hope it helps.</p>