title: Pandas datetime with Julian Day
body: <p>I tried searching for this and was surprised I couldn't find anything.  We use the term 'Julian Day' to refer to the day of the year irrespective of month (i.e. February 1st would be julian day 32).  I don't know if this is a regional term and maybe why I can't find any answers.</p>
  
  <p>Basically I have two files. One has a standard date format with year, month, day, hour.  The other has year, julian day, hour.  I am trying to align them using pandas DataFrame function and don't know what to do about the missing month data.  Is Pandas able to convert this natively?</p>
  
  <p>I am using python 3.3 and the newest version of Pandas.  </p>
  
  <p>Thanks!</p>