title: HoverTool on Bokeh: Time format issue (date do not appear correctly) x axis from datetime DF column in pandas
body: <p>Here the code I wrote.
  I took the data from pandas DF (not pasted here).
  The x values are from DF index columns that is a DateTime column.
  The issue that I want to resolve is in line:</p>
  
  <p>TOOLTIPS = [("index", "$index"),("(Time,Temperature)", "($x, $y)"),]</p>
  
  <p>when I have to change the $x format to a correct format in order to see the the time format in the hover window on the bokeh plot.</p>
  
  <p>see the python code</p>
  
  <pre><code>import datetime as dt
  from bokeh.plotting import figure, output_file, show
  
  from bokeh.layouts import gridplot
  from bokeh.models import ColumnDataSource, CDSView, BooleanFilter
  from bokeh.models import DatetimeTickFormatter
  
  
  
  x=df_bases.index
  
  y0=df_bases["base_1"]
  y1=df_bases["base_5"]
  y2=df_bases["base_12"]
  
  
  
  # output to static HTML file
  output_file("temperatures from thermocouples.html")
  
  
  
  # add some renderers
  
  output_file("Thermocouples temperature.html", title="Thermocouples temperature")
  
  TOOLTIPS = [("index", "$index"),("(Time,Temperature)", "($x, $y)"),]
  
  
  # create a new plot with a datetime axis type
  p = figure( tooltips=TOOLTIPS , plot_width=1250, plot_height=580, x_axis_type="datetime", x_axis_label='Time', 
             y_axis_label='Temperature [°C]', title="Thermocouples temperature") 
  
  
  p.line(x, y0, legend="thermocouple 1", line_width=1 , color='navy', alpha=1)
  p.line(x, y1, legend="thermocouple 5", color="green")
  p.line(x, y2, legend="thermocouple 12", line_width=1 , color='orange', alpha=1)#, line_dash="4 4")
  
  p.border_fill_color = "whitesmoke"
  
  
  p.xaxis.formatter=DatetimeTickFormatter(
      microseconds = ['%Y-%m-%d %H:%M:%S.%f'],
      milliseconds = ['%Y-%m-%d %H:%M:%S.%3N'],
      seconds = ["%Y-%m-%d %H:%M:%S"],
      minsec = ["%Y-%m-%d %H:%M:%S"],
      minutes = ["%Y-%m-%d %H:%M:%S"],
      hourmin = ["%Y-%m-%d %H:%M:%S"],
      hours=["%Y-%m-%d %H:%M:%S"],
      days=["%Y-%m-%d %H:%M:%S"],
      months=["%Y-%m-%d %H:%M:%S"],
      years=["%Y-%m-%d %H:%M:%S"],
  )
  
  
  p.title.align = 'center'
  
  
  
  
  
  # create a column data source for the plots to share
  source = ColumnDataSource(data=dict(x=x, y0=y0, y1=y1, y2=y2))
  
  # create a view of the source for one plot to use
  view = CDSView(source=source)
  
  
  
  
  # show the results
  show(p)
  </code></pre>