Have an error when web page access, but not in jupyter notebook

[JengkolRebus]

I am not an expert programmer.

I get an error like this when accessing the page that was created.
when run on jupyter notebook there is no problem. this happens when the web page is accessed.
it should show the DatePicker widget
anyone know why?

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-6-01df704f6fa5> in <module>
----> 1 hari_ini = datetime.now().date()
      2 days_in_month = calendar.monthrange(hari_ini.year, hari_ini.month)[1]
      3 besok = hari_ini + timedelta(days_in_month)
      4 
      5 print('Latitude: ', lat)

NameError: name 'datetime' is not defined

this is the program:
programs/konjungsibulan.ipynb

this is all the files in repository, if this helps:
https://github.com/JengkolRebus/nbinteract-files