title: Datetime x axis in bokeh.charts.Area
body: <p>Why I plot my data with a <code>datetime</code> series as x axis, it is interpreted as a <code>datetime</code> value, but the wrong one: my 2016 times are interpreted as  milliseconds after 1970-1-1. Code:</p>
  
  <pre><code>from __future__ import absolute_import, division, print_function
  from __future__ import unicode_literals
  
  from datetime import datetime
  import pandas as pd
  from bokeh.charts import Area, show, output_file
  
  df = pd.DataFrame()
  df['date'] = [datetime(2016, 1, 1), datetime(2016, 1, 2), datetime(2016, 1, 3)]
  df['v1'] = [1, 2, 3]
  df['v2'] = [4, 4, 3]
  
  p = Area(df, x='date', y=['v1', 'v2'], title="Area Chart",
           legend="top_left", xscale='datetime', stack=True,
           xlabel='time', ylabel='values')
  
  output_file("area.html", title="Area Chart")
  show(p)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/YuPm1.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YuPm1.png" alt="Area chart screenshot"></a></p>
  
  <p>Is there a way I can get <code>bokeh.charts.Area</code> recognize my <code>datetime</code> data, or do I have to construct the plot myself using <code>figure()</code>?</p>
  
  <p>Additional data: bokeh 0.11.1 on Python 2.7</p>