As the solution is hackish, I think using your own date/time widget with some JavaScript is more feasible.

I find myself referencing this post a lot, and found that the documentation defines a slightly less hacky way to override default widgets.

(No need to override the ModelForm’s __init__ method)

However, you still need to wire your JS and CSS appropriately as Carl mentions.

forms.py

from django import forms
from my_app.models import Product
from django.contrib.admin import widgets                                       


class ProductForm(forms.ModelForm):
    mydate = forms.DateField(widget=widgets.AdminDateWidget)
    mytime = forms.TimeField(widget=widgets.AdminTimeWidget)
    mydatetime = forms.SplitDateTimeField(widget=widgets.AdminSplitDateTime)

    class Meta:
        model = Product

Reference Field Types to find the default form fields.

My head code for 1.4 version(some new and some removed)

{% block extrahead %}

<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}admin/css/forms.css"/>
<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}admin/css/base.css"/>
<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}admin/css/global.css"/>
<link rel="stylesheet" type="text/css" href="{{ STATIC_URL }}admin/css/widgets.css"/>

<script type="text/javascript" src="/admin/jsi18n/"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/core.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/admin/RelatedObjectLookups.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/jquery.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/jquery.init.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/actions.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/calendar.js"></script>
<script type="text/javascript" src="{{ STATIC_URL }}admin/js/admin/DateTimeShortcuts.js"></script>

{% endblock %}

Yep, I ended up overriding the /admin/jsi18n/ url.

Here’s what I added in my urls.py. Make sure it’s above the /admin/ url

    (r'^admin/jsi18n', i18n_javascript),

And here is the i18n_javascript function I created.

from django.contrib import admin
def i18n_javascript(request):
  return admin.site.i18n_javascript(request)

Starting in Django 1.2 RC1, if you’re using the Django admin date picker widge trick, the following has to be added to your template, or you’ll see the calendar icon url being referenced through “/missing-admin-media-prefix/”.

{% load adminmedia %} /* At the top of the template. */

/* In the head section of the template. */
<script type="text/javascript">
window.__admin_media_prefix__ = "{% filter escapejs %}{% admin_media_prefix %}{% endfilter %}";
</script>

For Django >= 2.0

Note: Using admin widgets for date-time fields is not a good idea as admin style-sheets can conflict with your site style-sheets in case you are using bootstrap or any other CSS frameworks. If you are building your site on bootstrap use my bootstrap-datepicker widget django-bootstrap-datepicker-plus.

Step 1: Add javascript-catalog URL to your project’s (not app’s) urls.py file.

from django.views.i18n import JavaScriptCatalog

urlpatterns = [
    path('jsi18n', JavaScriptCatalog.as_view(), name='javascript-catalog'),
]

Step 2: Add required JavaScript/CSS resources to your template.

<script type="text/javascript" src="{% url 'javascript-catalog' %}"></script>
<script type="text/javascript" src="{% static '/admin/js/core.js' %}"></script>
<link rel="stylesheet" type="text/css" href="{% static '/admin/css/widgets.css' %}">
<style>.calendar>table>caption{caption-side:unset}</style><!--caption fix for bootstrap4-->
{{ form.media }}        {# Form required JS and CSS #}

Step 3: Use admin widgets for date-time input fields in your forms.py.

from django.contrib.admin import widgets
from .models import Product

class ProductCreateForm(forms.ModelForm):
    class Meta:
        model = Product
        fields = ['name', 'publish_date', 'publish_time', 'publish_datetime']
        widgets = {
            'publish_date': widgets.AdminDateWidget,
            'publish_time': widgets.AdminTimeWidget,
            'publish_datetime': widgets.AdminSplitDateTime,
        }

Complementing the answer by Carl Meyer, I would like to comment that you need to put that header in some valid block (inside the header) within your template.

{% block extra_head %}

<link rel="stylesheet" type="text/css" href="/media/admin/css/forms.css"/>
<link rel="stylesheet" type="text/css" href="/media/admin/css/base.css"/>
<link rel="stylesheet" type="text/css" href="/media/admin/css/global.css"/>
<link rel="stylesheet" type="text/css" href="/media/admin/css/widgets.css"/>

<script type="text/javascript" src="/admin/jsi18n/"></script>
<script type="text/javascript" src="/media/admin/js/core.js"></script>
<script type="text/javascript" src="/media/admin/js/admin/RelatedObjectLookups.js"></script>

{{ form.media }}

{% endblock %}

The below will also work as a last resort if the above failed

class PaymentsForm(forms.ModelForm):
    class Meta:
        model = Payments

    def __init__(self, *args, **kwargs):
        super(PaymentsForm, self).__init__(*args, **kwargs)
        self.fields['date'].widget = SelectDateWidget()

Same as

class PaymentsForm(forms.ModelForm):
    date = forms.DateField(widget=SelectDateWidget())

    class Meta:
        model = Payments

put this in your forms.py from django.forms.extras.widgets import SelectDateWidget

Another simple solution for Django 3 (3.2) in 2021 😉 cause andyw’s solution doesn’t work in Firefox…

{% load static %}

{% block extrahead %}
{{ block.super }}
<script type="text/javascript" src="{% static 'admin/js/cancel.js' %}"></script>
<link rel="stylesheet" type="text/css" href="{% static 'admin/css/forms.css' %}">
<script src="{% url 'admin:jsi18n' %}"></script>
<script src="{% static 'admin/js/jquery.init.js' %}"></script>
<script src="{% static 'admin/js/core.js' %}"></script>
{{ form.media }}
{% endblock %}

<form action="" method="post">
{% csrf_token %}
{{ form.as_p }}
<input type="submit" value="Сохранить">
</form>

and you’ll able to use your form.
example:

from django.contrib.admin import widgets
date_time = forms.SplitDateTimeField(widget=widgets.AdminSplitDateTime)

Here’s another 2020 solution, inspired by @Sandeep’s. Using the MinimalSplitDateTimeMultiWidget found in this gist, in our Form as below, we can use modern browser date and time selectors (via eg ‘type’: ‘date’). We don’t need any JS.

class EditAssessmentBaseForm(forms.ModelForm):
    class Meta:
        model = Assessment
        fields = '__all__'

    begin = DateTimeField(widget=MinimalSplitDateTimeMultiWidget())

What about just assigning a class to your widget and then binding that class to the JQuery datepicker?

Django forms.py:

class MyForm(forms.ModelForm):

  class Meta:
    model = MyModel

  def __init__(self, *args, **kwargs):
    super(MyForm, self).__init__(*args, **kwargs)
    self.fields['my_date_field'].widget.attrs['class'] = 'datepicker'

And some JavaScript for the template:

  $(".datepicker").datepicker();

Updated solution and workaround for SplitDateTime with required=False:

forms.py

from django import forms

class SplitDateTimeJSField(forms.SplitDateTimeField):
    def __init__(self, *args, **kwargs):
        super(SplitDateTimeJSField, self).__init__(*args, **kwargs)
        self.widget.widgets[0].attrs = {'class': 'vDateField'}
        self.widget.widgets[1].attrs = {'class': 'vTimeField'}  


class AnyFormOrModelForm(forms.Form):
    date = forms.DateField(widget=forms.TextInput(attrs={'class':'vDateField'}))
    time = forms.TimeField(widget=forms.TextInput(attrs={'class':'vTimeField'}))
    timestamp = SplitDateTimeJSField(required=False,)

form.html

<script type="text/javascript" src="/admin/jsi18n/"></script>
<script type="text/javascript" src="/admin_media/js/core.js"></script>
<script type="text/javascript" src="/admin_media/js/calendar.js"></script>
<script type="text/javascript" src="/admin_media/js/admin/DateTimeShortcuts.js"></script>

urls.py

(r'^admin/jsi18n/', 'django.views.i18n.javascript_catalog'),

I use this, it’s great, but I have 2 problems with the template:

1. I see the calendar icons twice for every filed in template.

2. And for TimeField I have ‘Enter a valid date.‘

   

models.py

from django.db import models
    name=models.CharField(max_length=100)
    create_date=models.DateField(blank=True)
    start_time=models.TimeField(blank=False)
    end_time=models.TimeField(blank=False)

forms.py

from django import forms
from .models import Guide
from django.contrib.admin import widgets

class GuideForm(forms.ModelForm):
    start_time = forms.DateField(widget=widgets.AdminTimeWidget)
    end_time = forms.DateField(widget=widgets.AdminTimeWidget)
    create_date = forms.DateField(widget=widgets.AdminDateWidget)
    class Meta:
        model=Guide
        fields=['name','categorie','thumb']

In Django 10.
myproject/urls.py:
at the beginning of urlpatterns

  from django.views.i18n import JavaScriptCatalog

urlpatterns = [
    url(r'^jsi18n/$', JavaScriptCatalog.as_view(), name='javascript-catalog'),
.
.
.]

In my template.html:

{% load staticfiles %}

    <script src="{% static "js/jquery-2.2.3.min.js" %}"></script>
    <script src="{% static "js/bootstrap.min.js" %}"></script>
    {# Loading internazionalization for js #}
    {% load i18n admin_modify %}
    <script type="text/javascript" src="{% url 'javascript-catalog' %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/jquery.init.js" %}"></script>

    <link rel="stylesheet" type="text/css" href="{% static "/admin/css/base.css" %}">
    <link rel="stylesheet" type="text/css" href="{% static "/admin/css/forms.css" %}">
    <link rel="stylesheet" type="text/css" href="{% static "/admin/css/login.css" %}">
    <link rel="stylesheet" type="text/css" href="{% static "/admin/css/widgets.css" %}">



    <script type="text/javascript" src="{% static "/admin/js/core.js" %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/SelectFilter2.js" %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/admin/RelatedObjectLookups.js" %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/actions.js" %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/calendar.js" %}"></script>
    <script type="text/javascript" src="{% static "/admin/js/admin/DateTimeShortcuts.js" %}"></script>

My Django Setup : 1.11
Bootstrap: 3.3.7

Since none of the answers are completely clear, I am sharing my template code which presents no errors at all.

Top Half of template:

{% extends 'base.html' %}
{% load static %}
{% load i18n %}

{% block head %}
    <title>Add Interview</title>
{% endblock %}

{% block content %}

<script type="text/javascript" src="{% url 'javascript-catalog' %}"></script>
<script type="text/javascript" src="{% static 'admin/js/core.js' %}"></script>
<link rel="stylesheet" type="text/css" href="{% static 'admin/css/forms.css' %}"/>
<link rel="stylesheet" type="text/css" href="{% static 'admin/css/widgets.css' %}"/>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" >
<script type="text/javascript" src="{% static 'js/jquery.js' %}"></script>

Bottom Half:

<script type="text/javascript" src="/admin/jsi18n/"></script>
<script type="text/javascript" src="{% static 'admin/js/vendor/jquery/jquery.min.js' %}"></script>
<script type="text/javascript" src="{% static 'admin/js/jquery.init.js' %}"></script>
<script type="text/javascript" src="{% static 'admin/js/actions.min.js' %}"></script>
{% endblock %}

June 3, 2020 (All answers didn’t worked, you can try this solution I used. Just for TimeField)

Use simple Charfield for time fields (start and end in this example) in forms.

forms.py

we can use Form or ModelForm here.

class TimeSlotForm(forms.ModelForm):
    start = forms.CharField(widget=forms.TextInput(attrs={'placeholder': 'HH:MM'}))
    end = forms.CharField(widget=forms.TextInput(attrs={'placeholder': 'HH:MM'}))

    class Meta:
        model = TimeSlots
        fields = ('start', 'end', 'provider')

Convert string input into time object in views.

import datetime
def slots():
    if request.method == 'POST':
        form = create_form(request.POST)
        if form.is_valid():                
            slot = form.save(commit=False)
            start = form.cleaned_data['start']
            end = form.cleaned_data['end']
            start = datetime.datetime.strptime(start, '%H:%M').time()
            end = datetime.datetime.strptime(end, '%H:%M').time()
            slot.start = start
            slot.end = end
            slot.save()

The most cleanest way (tested with Django 3.2):

from django.contrib import admin
from django.contrib.admin.widgets import AdminSplitDateTime
from django import forms


class MyCustomForm(forms.ModelForm):
    custom_datetime = forms.SplitDateTimeField(widget=AdminSplitDateTime())

    class Meta:
        model = MyModel
        fields = ("custom_datetime",)


class MyModelAdmin(admin.ModelAdmin):
    def my_custom_admin_view(self, request):
        form = MyCustomForm()
        admin_form = admin.helpers.AdminForm(form, [], {}, model_admin=self)
        media = self.media + admin_form.media
        context = {
            "media": media,
            "form": form,
        }
        return render(request, "my_custom_template.html", context)

In the my_custom_template.html:

{% extends "admin/base.html" %}

{% block extrastyle %}
{{ block.super }}
{{ media }}
{% endblock %}

{% block content %}
<form method="post">
{{ form.as_p  }}
<input type="submit" value="Submit" />
</form>
{% endblock %}