Django: A None DateInput does not pass through form validate. How can I fix it?

I use UpdateView and created a field called date_updated. When the user creates, e.g., a Group, there are zero updates. In models.py I defined:

date_updated = models.DateTimeField(null=True)

Then in forms.py I created the update form, e.g.,

class UpdateGroupForm(forms.ModelForm):

    class Meta:
        model = Group
        fields = ['name','date_updated']

In templates I call my form, as expected in the iteration {% for field in form %},
field.value = None for the specific field date_updated, and because of this I believe is not updating. In views.py I have the following in the UpdateGroup class

 def form_valid(self, form):
        if form.instance.owner == self.request.user:
            form.instance.date_updated = timezone.now()
            return super().form_valid(form)
        else:
            return super().form_invalid(form)

I tried to replace the empty value with a fake date considering in my templates the following:

{% if field.name == 'date_updated' and field.value == None %}
 <input type="date" name="date_updated" value="2000-01-01" format="yyyy-mm-dd" required disabled>                      
{% else %}

But it doesn't work also, I cannot validate the form and update my values with the first update.. What can I do? The only thing that works is to remove date_updated from forms.py, do the first update and then restore it in forms.py. Now because is not an empty Date everything works and I can proceed with a second update....so the first update is where I'm stuck

You can exclude the field date_updated from your form and template since you want it to be timezone.now(). This way you wont have to set a value for it like None. You should just keep this part form.instance.date_updated = timezone.now() which will do what you wanted.