title: Bokeh datetime via JS Adapter
body: <p>I have a Ajax data source in Bokeh that returns me an Array of dates in Unix format. I want to convert them to this: "2020-4-28 13:39:10" and then plot the figure with the dates as x. Rightnow my adapter returns the values as string and I use a DatetimeTickFormatter:</p>
  
  <pre><code>fig.xaxis.formatter = DatetimeTickFormatter(seconds=["%d/%m/ %H:%M:%S"],
                                              minutes=["%d/%m/ %H:%M:%S"],
                                              minsec=["%d/%m/ %H:%M:%S"],
                                              hours=["%d/%m/ %H:%M:%S"])
  </code></pre>
  
  <p>to get the right format. But the Bokeh fig doesnt accept the string as a datetime object and I get an error: "[bokeh] could not set initial ranges". </p>
  
  <p>How can I parse the data in a right format from the adapter to the figure? Thanks!
  I am using a python 3 flask application!</p>