Bokeh Datepicker interactions

Hello,
I want to add interactions with datepicker in bokeh.

After selecting particular date, data of that date should be reflect in the graph.

Is anyone have any idea/examples about adding interactions to datepicker in bokeh python. (with bokeh server or without bokeh server)

How can I display the change in date.

Thanks in advance.

-Gouri

I even tried following snippet but fail to return new date value from function

def callback(attr, old, new):
    print(type(old))
    print('old was {} and new is {}'.format(old, new))

ds = dt_pckr_strt.on_change('value', callback)