title: Python 3D plot with dates
body: <p>I am trying to make a 3D scatter plot that has the following axis: Price, Time and Dates. Essentially I want to plot the price vs the time for a single day and then do that for multiple days and stack them on an axis.</p>
  <p>Here is the code I have so far:</p>
  <pre><code> df=pd.read_csv(&quot;C:\\Desktop\\dat.csv&quot;)
   date=  df['date'].unique()
   dfd = pd.DataFrame(date)
   days= dfd.sort_values(0)
  
   fig= plt.figure()
   ax= fig.add_subplot(111, projection= '3d')
  
   xx = np.arange(len(days[0]))
   ys = [i+xx+(i*xx)**2 for i in range(len(days[0]))]
   colors = cm.rainbow(np.linspace(0, 1, len(ys)))
  
   for d,cc in zip(days[0],colors):
   
       td= df.loc[df['date'] == d]
       st= td[['time','price']]
  
       x = st['time']         
       y = st['price']
  
       x=list(x)
       y=list(y)
       ax.scatter(x,y,d,color=cc)
  
   plt.show()
  </code></pre>
  <p>The main problem is that x is a list with times and that d is a date. when I run the code matplotlib throws an error saying</p>
  <pre><code>ValueError: invalid literal for float(): 9:30:01
  </code></pre>
  <p>The dates are in the following format : 2017.04.12, time format : 9:30:01</p>
  <p>I am aware that I can set up tick labels for the date, but how can I handle the time?</p>
  <p>How can I plot this 3d plot if the axis indexes contain dates and times?</p>