title: Python: plotting time series data with two dependent date columns
body: <p>I'm a bit of a novice with Python and I've been googling this for about an hour now and can't seem to get anywhere - has anyone had this kind of problem before and managed told solve it?</p>
  
  <p>I'm trying to plot a time series data set with 1 metric across two date fields, which are both related.  For example, column A is the date, column B is the time slice within that date (ordinal)</p>
  
  <p>Here is an example of my data.</p>
  
  <pre><code>        date         period         variable
  2 2016-08-01  00:00 - 00:30         1
  3 2016-08-01  00:30 - 01:00         2
  4 2016-08-01  01:00 - 01:30         3
  5 2016-08-01  01:30 - 02:00         4
  6 2016-08-01  02:00 - 02:30         5
  </code></pre>
  
  <p>So I would want my x axis to show a combination of column A and column B, with column C on my y axis.</p>
  
  <p>Any ideas?</p>