title: Convert pandas column 'day of year' to datetime (%m-%d)?
body: <p>Suppose I have a Pandas DataFrame with a column which is the number of the day of the year (1 to 365). I would like to get a new column which is a datetime format (or any format which can be plotted as date index) which has only day and month (NO YEAR) value? That said the format of strftime would be %d-%m.</p>
  
  <p>So far I have managed to produce with strftime from a day numer 1 -> 01-01, the problem is that it is now a strip which is not useful for plotting my data...</p>
  
  <p>Any ideas how to get around the Year value?</p>