diff --git a/web/app/controllers/group.php b/web/app/controllers/group.php
index bc62b39..7855f51 100644
--- a/web/app/controllers/group.php
+++ b/web/app/controllers/group.php
@@ -95,41 +95,44 @@
 		<h2 class="card-title h4">
 			<?= UOJLocale::get('assignments') ?>
 		</h5>
-				<?php
-						$now = new DateTime();
-	echoLongTable(
-		['groups_assignments.list_id as list_id', 'lists.title as title', 'groups_assignments.end_time as end_time'],
-		'groups_assignments left join lists on lists.id = groups_assignments.list_id',
-		"groups_assignments.group_id = {$group['id']} and groups_assignments.end_time > addtime(now(), '-168:00:00')",
-		'order by end_time desc, list_id desc',
-		<<<EOD
-	<tr>
-		<th style="width:3em" class="text-center">ID</th>
-		<th style="width:12em">标题</th>
-		<th style="width:4em">状态</th>
-		<th style="width:8em">结束时间</th>
-	</tr>
+		<?php
+			echoLongTable(
+				[
+					'groups_assignments.list_id as list_id',
+					'lists.title as title',
+					'groups_assignments.end_time as end_time'
+				],
+				'groups_assignments left join lists on lists.id = groups_assignments.list_id',
+				"groups_assignments.group_id = {$group['id']} and groups_assignments.end_time > addtime(now(), '-168:00:00')",
+				'order by end_time desc, list_id desc',
+				<<<EOD
+			<tr>
+				<th style="width:3em" class="text-center">ID</th>
+				<th style="width:12em">标题</th>
+				<th style="width:4em">状态</th>
+				<th style="width:8em">结束时间</th>
+			</tr>
 EOD,
-		function($row) use ($group, $now) {
-			$end_time = DateTime::createFromFormat('Y-m-d H:i:s', $row['end_time']);
+				function($row) use ($group) {
+					$end_time = DateTime::createFromFormat('Y-m-d H:i:s', $row['end_time']);
 
-			echo '<tr>';
-			echo '<td class="text-center">', $row['list_id'], '</td>';
-			echo '<td>', '<a class="text-decoration-none" href="/group/', $group['id'], '/assignment/', $row['list_id'],'">', HTML::escape($row['title']), '</a>', '</td>';
-			if ($end_time < $now) {
-				echo '<td class="text-danger">已结束</td>';
-			} else {
-				echo '<td class="text-success">进行中</td>';
-			}
-			echo '<td>', $end_time->format('Y-m-d H:i:s'), '</td>';
-			echo '</tr>';
-		},
-		[
-			'echo_full' => true,
-			'div_classes' => ['table-responsive'],
-			'table_classes' => ['table', 'align-middle', 'mb-0'],
-		]
-	);
+					echo '<tr>';
+					echo '<td class="text-center">', $row['list_id'], '</td>';
+					echo '<td>', '<a class="text-decoration-none" href="/group/', $group['id'], '/assignment/', $row['list_id'],'">', HTML::escape($row['title']), '</a>', '</td>';
+					if ($end_time < UOJTime::$time_now) {
+						echo '<td class="text-danger">已结束</td>';
+					} else {
+						echo '<td class="text-success">进行中</td>';
+					}
+					echo '<td>', $end_time->format('Y-m-d H:i:s'), '</td>';
+					echo '</tr>';
+				},
+				[
+					'echo_full' => true,
+					'div_classes' => ['table-responsive'],
+					'table_classes' => ['table', 'align-middle', 'mb-0'],
+				]
+			);
 	?>
 	</div>
 </div>
diff --git a/web/app/controllers/group_manage.php b/web/app/controllers/group_manage.php
index a19dcaa..d06ed82 100644
--- a/web/app/controllers/group_manage.php
+++ b/web/app/controllers/group_manage.php
@@ -54,7 +54,8 @@
 					return '名称过长';
 				}
 
-				if (HTML::escape($title) === '') {
+				$title = HTML::escape($title);
+				if ($title === '') {
 					return '无效编码';
 				}
 
@@ -199,7 +200,6 @@ function(res) {
 EOD);
 		$add_new_assignment_form->runAtServer();
 
-		$now = new DateTime();
 		$hidden_time = new DateTime();
 		$hidden_time->sub(new DateInterval('P7D'));
 	} elseif ($cur_tab == 'users') {
@@ -349,7 +349,7 @@ EOD);
 		<th style="width:8em">操作</th>
 	</tr>
 EOD,
-						function($row) use ($group, $now, $hidden_time) {
+						function($row) use ($group, $hidden_time) {
 							$list = queryProblemList($row['list_id']);
 							$end_time = DateTime::createFromFormat('Y-m-d H:i:s', $row['end_time']);
 
@@ -363,7 +363,7 @@ EOD,
 							echo '</td>';
 							if ($end_time < $hidden_time) {
 								echo '<td class="text-secondary">已隐藏</td>';
-							} elseif ($end_time < $now) {
+							} elseif ($end_time < UOJTime::$time_now) {
 								echo '<td class="text-danger">已结束</td>';
 							} else {
 								echo '<td class="text-success">进行中</td>';
diff --git a/web/app/controllers/list_edit.php b/web/app/controllers/list_edit.php
index 3cccc09..0f79cd5 100644
--- a/web/app/controllers/list_edit.php
+++ b/web/app/controllers/list_edit.php
@@ -55,7 +55,8 @@
 					return '标题过长';
 				}
 
-				if (HTML::escape($title) === '') {
+				$title = HTML::escape($title);
+				if ($title === '') {
 					return '无效编码';
 				}
 
@@ -80,18 +81,18 @@
 				}
 
 				foreach ($tags_raw as $tag) {
-					$tag = trim($tag);
+					$tag = HTML::escape(trim($tag));
 
 					if (strlen($tag) == 0) {
 						continue;
 					}
 
 					if (strlen($tag) > 30) {
-						return '标签 “' . HTML::escape($tag) .'” 太长';
+						return '标签 “' . $tag .'” 太长';
 					}
 					
 					if (in_array($tag, $tags, true)) {
-						return '标签 “' . HTML::escape($tag) .'” 重复出现';
+						return '标签 “' . $tag .'” 重复出现';
 					}
 
 					$tags[] = $tag;
@@ -322,7 +323,6 @@ function(res) {
 EOD);
 		$add_new_assignment_form->runAtServer();
 		
-		$now = new DateTime();
 		$hidden_time = new DateTime();
 		$hidden_time->sub(new DateInterval('P7D'));
 	}
@@ -480,7 +480,7 @@ EOD,
 		<th style="width:8em">操作</th>
 	</tr>
 EOD,
-				function($row) use ($list, $now, $hidden_time) {
+				function($row) use ($list, $hidden_time) {
 					$group = queryGroup($row['group_id']);
 					$end_time = DateTime::createFromFormat('Y-m-d H:i:s', $row['end_time']);
 
@@ -489,7 +489,7 @@ EOD,
 					echo '<td>', '<a class="text-decoration-none" href="/group/', $group['id'], '">', HTML::escape($group['title']), '</a>', '</td>';
 					if ($end_time < $hidden_time) {
 						echo '<td class="text-secondary">已隐藏</td>';
-					} elseif ($end_time < $now) {
+					} elseif ($end_time < UOJTime::$time_now) {
 						echo '<td class="text-danger">已结束</td>';
 					} else {
 						echo '<td class="text-success">进行中</td>';
diff --git a/web/app/views/sidebar.php b/web/app/views/sidebar.php
index f573d29..4d024e2 100644
--- a/web/app/views/sidebar.php
+++ b/web/app/views/sidebar.php
@@ -56,15 +56,12 @@
 	<ul class="list-group list-group-flush">
 		<?php foreach ($assignments as $assignment): ?>
 			<li class="list-group-item">
-				<?php
-				$end_time = DateTime::createFromFormat('Y-m-d H:i:s', $assignment['end_time']);
-			$now = new DateTime();
-			?>
+				<?php $end_time = DateTime::createFromFormat('Y-m-d H:i:s', $assignment['end_time']); ?>
 				<a href="<?= HTML::url('/group/'.$assignment['group_id'].'/assignment/'.$assignment['list_id']) ?>" class="fw-bold text-decoration-none">
 					<?= $assignment['title'] ?>
-					<?php if ($end_time < $now): ?>
+					<?php if ($end_time < UOJTime::$time_now): ?>
 						<sup class="fw-normal text-danger">overdue</sup>
-					<?php elseif ($end_time->getTimestamp() - $now->getTimestamp() < 86400): ?>
+					<?php elseif ($end_time->getTimestamp() - UOJTime::$time_now->getTimestamp() < 86400): ?>
 						<sup class="fw-normal text-danger">soon</sup>
 					<?php endif ?>
 				</a>