Django type error: excepted string or byte types like object?

When I tried to publish blog an exception occurs "excepted string or bytes type object".I tried a lot but I don't know how to fix this . What I understand is that it is occuring because DateTimeField(default=timezone.now). I'm correct?

This is the error I m getting on writing py manage.py runserver:

File "C:\anaconda\envs\virblogEnv\lib\site-packages\django\db\models\fields\__init__.py", line 1318, in to_python
    parsed = parse_datetime(value)
  File "C:\anaconda\envs\virblogEnv\lib\site-packages\django\utils\dateparse.py", line 107, in parse_datetime
    match = datetime_re.match(value)
TypeError: expected string or bytes-like object
[] "GET / HTTP/1.1" 500 139276
Not Found: /favicon.ico
[] "GET /favicon.ico HTTP/1.1" 404 4283

Here is models.py:-

    from django.db import models
    from django.utils import timezone
    from django.urls import reverse
    
    
    class Post(models.Model):
        author=models.ForeignKey('auth.User',on_delete=models.CASCADE)
        title=models.CharField(max_length=200)
        text=models.TextField()
        created_date=models.DateTimeField(default=timezone.now)
        published_date=models.DateTimeField(blank=True,null=True)

    def publish(self):
        self.published_date=timezone.now
        self.save()

    def approve_comments(self):
        return self.comments.filter(approve_comments=True)

    def get_absolute_url(self):
        return reverse('post_detail',kwargs={'pk':self.pk})

    def __str__(self):
        return self.title


class Comment(models.Model):
    post=models.ForeignKey('blog.Post',related_name='comments',on_delete=models.CASCADE)
    author=models.CharField(max_length=200)
    text=models.TextField()
    created_date=models.DateTimeField(default=timezone.now)
    approve_comment=models.BooleanField(default=False)

    def approve(self):
        self.approved_comment=True
        self.save()

    def get_absolute_url(self):
        return reverse('post_list')


    def __str__(self):
        return self.text

Here is views.py:-

from django.shortcuts import render,get_object_or_404,redirect
from django.utils import timezone
from blog.forms import PostForm,CommentForm
from blog.models import Post,Comment 
from django.urls import reverse_lazy
from django.contrib.auth.decorators import login_required
from django.contrib.auth.mixins import LoginRequiredMixin
from django.views.generic import (TemplateView,ListView,DetailView,
                                    CreateView,UpdateView,DeleteView)

class AboutView(TemplateView):
    template_name='about.html'

class PostListView(ListView):
    model=Post

    #generating a query to db (so this means that grab all object filtered by published
    # by date in order of decending)
    def get_queryset(self):
        return Post.objects.filter(published_date__lte=timezone.now).order_by('-published_date')

class PostDetailView(DetailView):
    model=Post

class CreatePostView(LoginRequiredMixin,CreateView):
    login_url='/login/'
    redirect_field_name='blog/post_detail.html'
    form_class=PostForm
    model=Post


class PostUpdateView(LoginRequiredMixin,UpdateView):
    login_url='/login/'
    redirect_field_name='blog/post_detail.html'
    form_class=PostForm
    model=Post


class PostDeleteView(LoginRequiredMixin,DeleteView):
    model=Post

    success_url= reverse_lazy('post_list')

class DraftListView(LoginRequiredMixin,ListView):
    login_url='/login/'
    redirect_field_name='blog/post_list.html'
    model='Post'

    def get_queryset(self):
        return Post.objects.filter(published_date__isnull=True).order_by('created_date')


@login_required
def post_publish(request,pk):
    post=get_object_or_404(Post,pk=pk)
    post.publish()
    return redirect('post_detail',pk=pk)


@login_required
def add_comment_to_post(request,pk):
    post=get_object_or_404(Post,pk=pk)

    if request.method=='POST':
        form=CommentForm(request.POST)
        if form.is_valid():
            comment=form.save(commit=False)
            comment.post=post
            comment.save()
            return redirect('post_detail',pk=post.pk)

        else:
            form=CommentForm()

        return render(request,'blog/comment_form.html',{'form':form})


@login_required
def comment_approve(request,pk):
    comment=get_object_or_404(Comment,pk=pk)
    comment.approve()

    return redirect('post_detail',pk=comment.post.pk)

@login_required
def comment_remove(request,pk):
    comment=get_object_or_404(Comment,pk=pk)
    post_pk=comment.post.pk
    comment.delete()
    return redirect('post_detail',pk=post_pk)

Please help me!!