diff --git a/packages/backend/test/unit/AnnouncementService.ts b/packages/backend/test/unit/AnnouncementService.ts
index 5fe41d196..f2aa5d35e 100644
--- a/packages/backend/test/unit/AnnouncementService.ts
+++ b/packages/backend/test/unit/AnnouncementService.ts
@@ -35,7 +35,7 @@ describe('AnnouncementService', () => {
 	function createUser(data: Partial<MiUser> = {}) {
 		const un = secureRndstr(16);
 		return usersRepository.insert({
-			id: genAidx(new Date()),
+			id: genAidx(Date.now()),
 			username: un,
 			usernameLower: un,
 			...data,
diff --git a/packages/backend/test/unit/RoleService.ts b/packages/backend/test/unit/RoleService.ts
index 41a2e49ed..8b5e3163c 100644
--- a/packages/backend/test/unit/RoleService.ts
+++ b/packages/backend/test/unit/RoleService.ts
@@ -37,7 +37,7 @@ describe('RoleService', () => {
 	function createUser(data: Partial<MiUser> = {}) {
 		const un = secureRndstr(16);
 		return usersRepository.insert({
-			id: genAidx(new Date()),
+			id: genAidx(Date.now()),
 			username: un,
 			usernameLower: un,
 			...data,
@@ -47,7 +47,7 @@ describe('RoleService', () => {
 
 	function createRole(data: Partial<MiRole> = {}) {
 		return rolesRepository.insert({
-			id: genAidx(new Date()),
+			id: genAidx(Date.now()),
 			updatedAt: new Date(),
 			lastUsedAt: new Date(),
 			description: '',
diff --git a/packages/backend/test/unit/activitypub.ts b/packages/backend/test/unit/activitypub.ts
index 2e9454927..c418e8413 100644
--- a/packages/backend/test/unit/activitypub.ts
+++ b/packages/backend/test/unit/activitypub.ts
@@ -23,6 +23,7 @@ import { secureRndstr } from '@/misc/secure-rndstr.js';
 import { DownloadService } from '@/core/DownloadService.js';
 import { MetaService } from '@/core/MetaService.js';
 import type { MiRemoteUser } from '@/models/User.js';
+import { genAidx } from '@/misc/id/aidx.js';
 import { MockResolver } from '../misc/mock-resolver.js';
 
 const host = 'https://host1.test';
@@ -200,7 +201,7 @@ describe('ActivityPub', () => {
 	describe('Renderer', () => {
 		test('Render an announce with visibility: followers', () => {
 			rendererService.renderAnnounce(null, {
-				createdAt: new Date(0),
+				id: genAidx(Date.now()),
 				visibility: 'followers',
 			} as MiNote);
 		});
diff --git a/packages/backend/test/unit/misc/id.ts b/packages/backend/test/unit/misc/id.ts
index 57b4ea994..59783a9fa 100644
--- a/packages/backend/test/unit/misc/id.ts
+++ b/packages/backend/test/unit/misc/id.ts
@@ -14,44 +14,44 @@ import { ulidRegExp, parseUlid } from '@/misc/id/ulid.js';
 
 describe('misc:id', () => {
 	test('aid', () => {
-		const date = new Date();
+		const date = Date.now();
 		const gotAid = genAid(date);
 		expect(gotAid).toMatch(aidRegExp);
-		expect(parseAid(gotAid).date.getTime()).toBe(date.getTime());
+		expect(parseAid(gotAid).date.getTime()).toBe(date);
 	});
 
 	test('aidx', () => {
-		const date = new Date();
+		const date = Date.now();
 		const gotAidx = genAidx(date);
 		expect(gotAidx).toMatch(aidxRegExp);
-		expect(parseAidx(gotAidx).date.getTime()).toBe(date.getTime());
+		expect(parseAidx(gotAidx).date.getTime()).toBe(date);
 	});
 
 	test('meid', () => {
-		const date = new Date();
+		const date = Date.now();
 		const gotMeid = genMeid(date);
 		expect(gotMeid).toMatch(meidRegExp);
-		expect(parseMeid(gotMeid).date.getTime()).toBe(date.getTime());
+		expect(parseMeid(gotMeid).date.getTime()).toBe(date);
 	});
 
 	test('meidg', () => {
-		const date = new Date();
+		const date = Date.now();
 		const gotMeidg = genMeidg(date);
 		expect(gotMeidg).toMatch(meidgRegExp);
-		expect(parseMeidg(gotMeidg).date.getTime()).toBe(date.getTime());
+		expect(parseMeidg(gotMeidg).date.getTime()).toBe(date);
 	});
 
 	test('objectid', () => {
-		const date = new Date();
+		const date = Date.now();
 		const gotObjectId = genObjectId(date);
 		expect(gotObjectId).toMatch(objectIdRegExp);
-		expect(Math.floor(parseObjectId(gotObjectId).date.getTime() / 1000)).toBe(Math.floor(date.getTime() / 1000));
+		expect(Math.floor(parseObjectId(gotObjectId).date.getTime() / 1000)).toBe(Math.floor(date / 1000));
 	});
 
 	test('ulid', () => {
-		const date = new Date();
-		const gotUlid = ulid(date.getTime());
+		const date = Date.now();
+		const gotUlid = ulid(date);
 		expect(gotUlid).toMatch(ulidRegExp);
-		expect(parseUlid(gotUlid).date.getTime()).toBe(date.getTime());
+		expect(parseUlid(gotUlid).date.getTime()).toBe(date);
 	});
 });