diff --git a/app/ListItem.tsx b/app/ListItem.tsx
index 7a06920..ee900d6 100644
--- a/app/ListItem.tsx
+++ b/app/ListItem.tsx
@@ -1,10 +1,10 @@
 import { StarIcon } from '@heroicons/react/24/solid';
-import dayjs from 'dayjs';
 import Link from 'next/link';
 import { generateSummaryEntity, SummaryEntity } from 'search-summary';
 import { twMerge } from 'tailwind-merge';
 import { Entry } from '../domain/Entry';
 import { SearchQuery } from '../domain/SearchQuery';
+import dayjs from '../infra/dayjs';
 import { Skelton } from './_components/Skelton';
 import { Tags } from './_components/Tags';
 
diff --git a/app/Preview.tsx b/app/Preview.tsx
index d18116e..8242aed 100644
--- a/app/Preview.tsx
+++ b/app/Preview.tsx
@@ -1,6 +1,6 @@
 import { StarIcon } from '@heroicons/react/24/solid';
-import dayjs from 'dayjs';
 import { Entry } from '../domain/Entry';
+import dayjs from '../infra/dayjs';
 import { MarkdownText } from './_components/MarkdownText';
 
 export const Preview = (props: { entry: Entry }) => {
@@ -8,7 +8,7 @@ export const Preview = (props: { entry: Entry }) => {
     <div className="mx-auto max-w-3xl px-10 pt-10 text-gray-700 dark:bg-gray-800 dark:text-gray-300">
       <div className="mb-3 flex flex-row items-center space-x-3">
         <p className="text-xl text-gray-500 dark:text-gray-400">
-          {dayjs(props.entry.createdAt).format('YYYY-MM-DD HH:mm')}
+          {dayjs(props.entry.createdAt).tz().format('YYYY-MM-DD HH:mm')}
         </p>
 
         {props.entry.starred && (
diff --git a/app/[uuid]/Article.tsx b/app/[uuid]/Article.tsx
index ee2b598..f00a8f2 100644
--- a/app/[uuid]/Article.tsx
+++ b/app/[uuid]/Article.tsx
@@ -1,6 +1,6 @@
-import dayjs from 'dayjs';
 import { PropsWithChildren } from 'react';
 import { Entry } from '../../domain/Entry';
+import dayjs from '../../infra/dayjs';
 import { MarkdownText } from '../_components/MarkdownText';
 import { Skelton } from '../_components/Skelton';
 import { Tags } from '../_components/Tags';
@@ -19,7 +19,7 @@ export const Article = (props: { entry: Entry }) => {
       <MarkdownText>{props.entry.text}</MarkdownText>
       <div className="mt-3 flex flex-row space-x-4">
         <p className="text-gray-600 dark:text-gray-400">
-          {dayjs(props.entry.createdAt).format('YYYY-MM-DD')}
+          {dayjs(props.entry.createdAt).tz().format('YYYY-MM-DD')}
         </p>
         <Tags tags={props.entry.tags} />
       </div>
diff --git a/app/[uuid]/ArticleHeader.tsx b/app/[uuid]/ArticleHeader.tsx
index f4783cb..96ae942 100644
--- a/app/[uuid]/ArticleHeader.tsx
+++ b/app/[uuid]/ArticleHeader.tsx
@@ -36,7 +36,7 @@ export const ArticleHeader = ({
   const router = useRouter();
   const { register, setValue, control, handleSubmit } = useForm<Form>({
     defaultValues: {
-      createdAt: dayjs(entry.createdAt).format('YYYY-MM-DDTHH:mm'),
+      createdAt: dayjs(entry.createdAt).tz().format('YYYY-MM-DDTHH:mm'),
       tags: entry.tags,
       starred: entry.starred,
     },
@@ -102,7 +102,7 @@ export const ArticleHeader = ({
       <Popover
         triggerButton={
           <Button rightIcon={<ChevronDownIcon />} className="w-auto">
-            {dayjs(entry.createdAt).format('YYYY-MM-DD')}
+            {dayjs(entry.createdAt).tz().format('YYYY-MM-DD')}
           </Button>
         }
         side="bottom"
diff --git a/domain/Entry.ts b/domain/Entry.ts
index 965b291..f5f591f 100644
--- a/domain/Entry.ts
+++ b/domain/Entry.ts
@@ -1,5 +1,6 @@
 import crypto from 'crypto';
-import dayjs, { Dayjs } from 'dayjs';
+import { Dayjs } from 'dayjs';
+import dayjs from '../infra/dayjs';
 
 export type Entry = {
   text: string;
@@ -23,8 +24,8 @@ export const newEntry = (props: {
     starred: props.starred ?? false,
     uuid: props.uuid ?? crypto.randomUUID().replace(/-/g, '').toUpperCase(),
     tags: props.tags ?? [],
-    createdAt: dayjs(props.createdAt).format(), // current time if empty
-    modifiedAt: dayjs(props.modifiedAt).format(),
+    createdAt: dayjs(props.createdAt).tz().format(), // with timezone
+    modifiedAt: dayjs(props.modifiedAt).tz().format(),
   };
 };
 
@@ -33,7 +34,7 @@ export const extractTagHistory = (posts: Entry[]): string[] => [
 ]; // uniq
 
 // 基準になる日時
-const baseDate = dayjs('2023-06-23T02:25:00+09:00');
+const baseDate = dayjs.tz('2023-06-23T02:25');
 
 export const sampleEntries: Entry[] = [
   newEntry({
diff --git a/domain/__tests__/Tag.test.ts b/domain/__tests__/Tag.test.ts
index 1a884d8..531a667 100644
--- a/domain/__tests__/Tag.test.ts
+++ b/domain/__tests__/Tag.test.ts
@@ -1,5 +1,5 @@
 import assert from 'assert';
-import dayjs from 'dayjs';
+import dayjs from '../../infra/dayjs';
 import { newEntry } from '../Entry';
 import { tagNameToId, entriesTagToABs } from '../Tag';
 
diff --git a/infra/__tests__/entryRepository.test.ts b/infra/__tests__/entryRepository.test.ts
index 7d1596f..a63cf90 100644
--- a/infra/__tests__/entryRepository.test.ts
+++ b/infra/__tests__/entryRepository.test.ts
@@ -1,6 +1,6 @@
 import assert from 'assert';
-import dayjs from 'dayjs';
 import { newEntry } from '../../domain/Entry';
+import dayjs from '../../infra/dayjs';
 import * as entryRepository from '../entryRepository';
 
 describe('Query:entriesRepository', () => {
diff --git a/infra/__tests__/queue.test.ts b/infra/__tests__/queue.test.ts
index 97b357a..02e38af 100644
--- a/infra/__tests__/queue.test.ts
+++ b/infra/__tests__/queue.test.ts
@@ -1,6 +1,6 @@
 import assert from 'assert';
-import dayjs from 'dayjs';
 import { newEntry } from '../../domain/Entry';
+import dayjs from '../../infra/dayjs';
 import * as entryRepository from '../entryRepository';
 import { entriesQueue } from '../queue';