diff --git a/packages/hydrooj/src/libs.ts b/packages/hydrooj/src/libs.ts
index 4076f32ca..1ec83304d 100644
--- a/packages/hydrooj/src/libs.ts
+++ b/packages/hydrooj/src/libs.ts
@@ -1,8 +1,5 @@
 import AdmZip from 'adm-zip';
-import fs from 'fs-extra';
-import yaml from 'js-yaml';
 import _ from 'lodash';
-import moment from 'moment-timezone';
 import Schema from 'schemastery';
 import superagent from 'superagent';
 import { Context } from './context';
@@ -12,7 +9,7 @@ export * from './utils';
 export * from './interface';
 export * from './typeutils';
 export {
-    Schema, yaml, fs, AdmZip, superagent, _, moment,
+    Schema, AdmZip, superagent, _,
 };
 export const definePlugin = <T = never>(args: {
     using?: keyof Context[];
diff --git a/packages/hydrooj/src/model/discussion.ts b/packages/hydrooj/src/model/discussion.ts
index a554bba43..a891b62e3 100644
--- a/packages/hydrooj/src/model/discussion.ts
+++ b/packages/hydrooj/src/model/discussion.ts
@@ -1,5 +1,5 @@
 import { omit } from 'lodash';
-import moment from 'moment';
+import moment from 'moment-timezone';
 import { FilterQuery, ObjectID } from 'mongodb';
 import { Context } from '../context';
 import { DiscussionNodeNotFoundError, DocumentNotFoundError } from '../error';
diff --git a/packages/hydrooj/src/model/storage.ts b/packages/hydrooj/src/model/storage.ts
index 49b32a50f..f069f0151 100644
--- a/packages/hydrooj/src/model/storage.ts
+++ b/packages/hydrooj/src/model/storage.ts
@@ -1,7 +1,7 @@
 import { extname } from 'path';
 import { escapeRegExp } from 'lodash';
 import { lookup } from 'mime-types';
-import moment from 'moment';
+import moment from 'moment-timezone';
 import { nanoid } from 'nanoid';
 import type { Readable } from 'stream';
 import * as bus from '../service/bus';
diff --git a/packages/hydrooj/src/upgrade.ts b/packages/hydrooj/src/upgrade.ts
index 606da6874..c5ba447dd 100644
--- a/packages/hydrooj/src/upgrade.ts
+++ b/packages/hydrooj/src/upgrade.ts
@@ -3,7 +3,7 @@
 /* eslint-disable @typescript-eslint/naming-convention */
 import yaml from 'js-yaml';
 import { pick } from 'lodash';
-import moment from 'moment';
+import moment from 'moment-timezone';
 import { ObjectID } from 'mongodb';
 import { buildContent } from './lib/content';
 import { Logger } from './logger';
diff --git a/packages/utils/lib/utils.ts b/packages/utils/lib/utils.ts
index 7451df4c9..cc3fcbe38 100644
--- a/packages/utils/lib/utils.ts
+++ b/packages/utils/lib/utils.ts
@@ -4,7 +4,7 @@ import path from 'path';
 import { Duplex } from 'stream';
 import { inspect } from 'util';
 import fs from 'fs-extra';
-import { isMoment, Moment } from 'moment-timezone';
+import moment, { isMoment, Moment } from 'moment-timezone';
 import { ObjectID } from 'mongodb';
 import Logger from 'reggol';
 export * as yaml from 'js-yaml';
@@ -18,7 +18,7 @@ Logger.targets[0].label = {
     margin: 1,
 };
 
-export { Logger };
+export { Logger, moment };
 
 const encrypt = (algorithm, content) => crypto.createHash(algorithm).update(content).digest('hex');
 export const sha1 = (content: string) => encrypt('sha1', content);