title: Using Statsmodel ARIMA without dates
body: <p>I have a time series but I do not have any Dates. </p>
  
  <p>I know that the collected data is evenly spaced.</p>
  
  <p>Statsmodel ARIMA assumes that I must have dates and throws the following error: </p>
  
  <pre><code>ValueError: Given a pandas object and the index does not contain dates
  </code></pre>
  
  <p>Is it not possible to utilize ARIMA without knowing the dates? </p>