title: Pandas pivot table - setting the months index as chronological order, not alphabetical
body: <p>I am trying to make a heatmap using seaborn, with months as the y-axis. However I see that if I call calendar.head() after making the pivot table, that the pivot table has the months column in alphabetical order instead of the chronological order which I have in my csv file. Is there anyway of stopping pandas from ordering it alphabetically, or to reorder it back to chronological order?</p>
  
  <pre><code>import seaborn as sns
  
  df = pd.read_csv("C:/Users/Paul/Desktop/calendar.csv")
  
  calendar = df.pivot("Month", "Year", "hPM2.5")
  
  ax = sns.heatmap(calendar, annot=True, fmt="d")
  </code></pre>