title: get number of files modified last month
body: <p>I'm trying to get a count of how many PDFs were created last month.  I'm using the following command but it's returning <code>0</code></p>
  
  <pre><code>find . -name '*.pdf' -mtime +46 ! -mtime +30 | wc -l
  </code></pre>
  
  <p>I'm in the correct directory and it seems like the logic is correct... any ideas on why this isn't working?  Is there an easier way, say to pass the specific month I'm looking for instead of trying to calculate days like this?</p>