title: Python Pandas -- melt, pivot, transpose on multiple columns
body: <p>I have a dataframe that looks like shown below. Index is years (1964 to 2016, non-unique, each year repeats 31 times), 1st column is days (1 to 31) and columns 2 to 13 are months (1 to 12)</p>
  
  <p>Question is: how do I convert this to a Pandas series (or single column df) with pd.DatetimeIndex dates? I've tried using groupby, melt, pivot and transpose, but I am not able to figure out the correct syntax and the documentation is not clear. Thanks a lot for your help! </p>
  
  <p><a href="https://i.stack.imgur.com/4CeEj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/4CeEj.png" alt="Dataframe"></a></p>