Djangoのフィルター機能の自作がエラーを吐きます。

前提

pythonのDjangoを用いてWebアプリ構築の勉強をしています。
フィルター機能の自作を行いたいのですが、以下のエラー文が出てしまいます。
TemplateSyntaxError: 'custom_tags' is not a registered tag library.

ディレクトリとファイルの階層は以下のようになっています。

WebAplication                                                                                                
  └── TemplateExam                                            
       ├──  static                                                                                                   
       ├──  TemplateApp                        
       |        ├── migrations  
       |        ├── templatetags                                                         
       |        |      ├── __pycache__  
       |        |      ├── __init__.py   
       |        |      └── custom_tags.py    
       |        ├── __init__.py                            
       |        ├── admin.py                         
       |        ├── apps.py                            
       |        ├── models.py                              
       |        ├── tests.py                           
       |        └── views.py                           
       ├─  TemplateExam     
       ├─  templates   
       |        ├── base.html                           
       |        ├── home.html                  
       |        ├── member_detail.html                          
       |        └── members.html                                                                             
       ├─  db.sqlite3                               
       └── manage.py

フィルター機能を使っている箇所

custom_tags.pyで作成したフィルター(calcurate_datetime_to_now)をmember_detail.htmlの１０行目で利用しています。

custom_tags.py

python
1from django import template
2from datetime import datetime
3import math
4
5registar = template.Library()
6
7@registar.filter(name='calcurate_datetime_to_now')
8def calcurate_datetime_to_now(value):
9    join_datetime = datetime.strptime(value, ' %Y / %m / %d')
10    now_datetime = datetime.now()
11    # timedelta class
12    diff_datetime = now_datetime - join_datetime
13    diff_days = diff_datetime.days
14    diff_years = math.floor(diff_days / 365)
15    diff_months = math.floor((diff_days - 365 * diff_years) / 30)
16    return f'{diff_years}年　{diff_months}ヶ月'

member_detail.html

html
1{% extends "base.html" %}
2{% block title %}メンバー詳細{{block.super}}{% endblock %}
3{% block content %}
4{% load static %}
5{% load custom_tags %} <!-- 新規追加 -->
6<h1>メンバー詳細画面</h1>
7  <img src="{% static member.picture_path %}">
8  <p>名前：{{member.name}}</p>
9  <p>入部日：{{member.join_at}}</p>
10  <p>入部から：{{member.join_at|calcurate_datetime_to_now}}</p> <!-- 新規追加 -->
11{% endblock %}

自作したフィルター機能の部分を除いた状態(member_detail.htmlの５，１０行目を除いた状態）だと正常に動きます。

エラーはmember_detail.htmlの{% load static %}の部分に問題があると記載されているのですが、原因がつかめません。

エラー全文

Internal Server Error: /app/member/1
Traceback (most recent call last):
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\defaulttags.py", line 1027, in find_library
    return parser.libraries[name]
KeyError: 'custom_tags'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\core\handlers\exception.py", line 55, in inner
    response = get_response(request)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\core\handlers\base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\xxx\OneDrive - maebashi-it.ac.jp\プログラミング\study\study_programing\Python\my_program\django\section5-Template\question116-121\TemplateExa
m\TemplateApp\views.py", line 40, in member
    return render(request, 'member_detail.html', context={
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\shortcuts.py", line 24, in render
    content = loader.render_to_string(template_name, context, request, using=using)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loader.py", line 61, in render_to_string
    template = get_template(template_name, using=using)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loader.py", line 15, in get_template
    return engine.get_template(template_name)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\backends\django.py", line 34, in get_template
    return Template(self.engine.get_template(template_name), self)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\engine.py", line 175, in get_template
    template, origin = self.find_template(template_name)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\engine.py", line 157, in find_template
    template = loader.get_template(name, skip=skip)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loaders\cached.py", line 57, in get_template
    template = super().get_template(template_name, skip)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loaders\base.py", line 28, in get_template
    return Template(
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 154, in __init__
    self.nodelist = self.compile_nodelist()
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 200, in compile_nodelist
    return parser.parse()
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 513, in parse
    raise self.error(token, e)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 511, in parse
    compiled_result = compile_func(self, token)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loader_tags.py", line 293, in do_extends
    nodelist = parser.parse()
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 513, in parse
    raise self.error(token, e)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 511, in parse
    compiled_result = compile_func(self, token)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\loader_tags.py", line 232, in do_block
    nodelist = parser.parse(("endblock",))
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 513, in parse
    raise self.error(token, e)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\base.py", line 511, in parse
    compiled_result = compile_func(self, token)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\defaulttags.py", line 1089, in load
    lib = find_library(parser, name)
  File "C:\Users\xxx\xxx\envs\xxx\lib\site-packages\django\template\defaulttags.py", line 1029, in find_library
    raise TemplateSyntaxError(
django.template.exceptions.TemplateSyntaxError: 'custom_tags' is not a registered tag library. Must be one of:
admin_list
admin_modify
admin_urls
cache
i18n
l10n
log
static
tz

ちなみにurls.py、views.py、settings.py、base.htmlはそれぞれ以下のようになっています。

TemplateExam/TemplateExam/urls.py

python
1from django.contrib import admin
2from django.urls import path, include
3
4urlpatterns = [
5    path("admin/", admin.site.urls),
6    path('app/', include('TemplateApp.urls')),
7]

TemplateExam\TemplateApp\urls.py(ファイルを新規作成)

python
1from django.urls import path
2from . import views
3
4
5app_name = 'app'
6urlpatterns = [
7  path('home', views.home, name='home'),
8  path('members', views.members, name='members'),#メンバー一覧を表示するURLのパス
9  path('member/<int:id>', views.member, name='member'), #メンバーの詳細画面
10]

TemplateExam\TemplateApp\views.py(追加記入)

python
1# 関数の作成
2
3from django.shortcuts import render
4
5# Create your views here.
6
7#メンバー一覧を表示するための情報
8class Member:
9'''
10join_at:入部した日
11picture_path:画像ファイルのパス
12'''
13  def __init__(self, id, name, join_at, picture_path):
14    self.id = id
15    self.name = name
16    self.join_at = join_at
17    self.picture_path = picture_path
18
19#メンバー一覧を表示するためのリスト
20member_list = [
21  Member(0,'Taro' ,'2018/04/01' ,'img/taro.jpg' ),
22  Member(1,'Jiro' ,'2019/04/01' ,'img/jiro.jpg' ),
23  Member(2,'Hanako' ,'2019/05/01' ,'img/hanako.jpg' ),
24  Member(3,'Yoshiko' ,'2018/10/01' ,'img/yoshiko.jpg' ),
25]
26
27
28
29#ホーム画面
30def home(request):
31  return render(request, 'home.html')
32
33#メンバー一覧
34def members(request):
35  return render(request, 'members.html', context={
36    'members':member_list
37  })
38
39#メンバーの画面詳細
40def member(request, id):
41  return render(request, 'member_detail.html', context={
42    'member':member_list[id]
43  })

TemplateExam\TemplateExam\settings.py

python
1from pathlib import Path
2import os       #--------新規追加
3
4# Build paths inside the project like this: BASE_DIR / 'subdir'.
5BASE_DIR = Path(__file__).resolve().parent.parent
6TEMPLATE_DIR = os.path.join(BASE_DIR, 'templates')  #----新規追加
7STATIC_DIR = os.path.join(BASE_DIR, 'static')       #----新規追加
8
9'''
10省略
11'''
12
13#TEMPLATE_DIRとSTATIC_DIRをそれぞれ指定
14TEMPLATES = [
15    {
16        "BACKEND": "django.template.backends.django.DjangoTemplates",
17        "DIRS": [TEMPLATE_DIR], #-------新規追加
18        "APP_DIRS": True,
19        "OPTIONS": {
20            "context_processors": [
21                "django.template.context_processors.debug",
22                "django.template.context_processors.request",
23                "django.contrib.auth.context_processors.auth",
24                "django.contrib.messages.context_processors.messages",
25            ],
26        },
27    },
28]
29
30'''
31省略
32'''
33
34#最後尾に新規追加
35STATICFILES_DIRS = [
36    STATIC_DIR,
37]