title: whenever gem and scheduling a job every n min starting at an offset
body: <p>For staggering purposes I am trying to schedule jobs an a 2 minute offset that run every 5 mins. That is I want 1 job to run 1,6,11,16.. and the other one to run at 2,7,12,17...</p>
  
  <p>I couldn't find an example to do this. So I tried:</p>
  
  <pre><code>every 5.minutes, :at=&gt; 1 do
   command "echo 'you can use raw cron sytax too'"
  end 
  </code></pre>
  
  <p>This seems to work but all the ':at' examples look to be expecting a time in a string format. Is the above valid to do or is just happens to work and the every option doesn't really support a starting time.</p>