title: Bokeh TimeSeries Tooltip Date Shows as:?
body: <p>I've looked at pretty much every single other stackoverflow question about this, but I can't get my date to show up in the tooltip:</p>
  
  <pre><code>dfx = dfx[['FullDate','DLM','DGO']]
  dfx['Date'] = pd.to_datetime(dfx['FullDate'])
  dfx['FullDate'] = dfx['FullDate'].astype(str)
  
  p = TimeSeries(dfx, x='Date', tools='hover',plot_width=900, plot_height=350, xlabel='Date'
                 ,ylabel='Cumulative Returns',source=ColumnDataSource(dfx))
  
  hover = p.select(dict(type=HoverTool))
  hover.tooltips = [("Date", "@FullDate"),("Value", "$y{1.111}")]
  
  show(p)
  </code></pre>
  
  <p>Produces this:</p>
  
  <p><a href="https://i.stack.imgur.com/lYm1Y.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lYm1Y.png" alt="enter image description here"></a></p>
  
  <p>I can show all the variations of this code I've done, but they all produce the same result.</p>
  
  <p>My <code>dfx['FullDate']</code> column are all strings. I feel like I'm missing something obvious.</p>
  
  <p>Thanks</p>