class Post(models.Model):
    title = models.CharField(max_length=255)
    content = models.TextField()
    image = models.ImageField(blank=True, null=True)
    publication_date = models.DateField(default=datetime.date.today)
    expiring_date = models.DateField()

class PostForm(forms.models.ModelForm):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.instance.publication_date = datetime.date.today()

    class Meta:
        model = Post
        exclude = ['publication_date']
        widgets = {
            'title': forms.fields.TextInput(attrs={
                'class': 'form-control'
            }),
            'content': forms.Textarea(attrs={
                'class': 'form-control'
            }),
            'image': forms.fields.FileInput(attrs={
                'class': 'form-control'
            }),
            'expiring_date': forms.fields.DateInput(attrs={
                'input_type': 'date',
                'class': 'form-control'
            }),
        }

def edit(request, post_id):
        post = get_object_or_404(Post, pk=post_id)
        form = PostForm(instance=post)
        return render(request, 'posts/edit.html', {'form': form})

{% block content %}
<div class="row">
    <div class="col-md-12">
      <div class="card animated materialU animation-delay-5">
        <div class="card-block card-block-big">
          <form action="{% url 'posts:update' %}" method="post" enctype='multipart/form-data'>
            {{ form }}
            <input type="submit" name="save changes" value="Save Changes" class="btn btn-success">
            {% csrf_token %}
          </form>
        </div>
      </div>
  </div>
</div>
{% endblock %}