Add Chinese for custom date/time format (#4853)

* Translate item_timeFormat in Chinese

* Update sub.php

* Update sub.php

app/i18n/zh-cn/sub.php

@@ -99,8 +99,8 @@ return array(
 					'help' => '例如 <code>descendant::img/@src</code>',
 				),
 				'item_timeFormat' => array(
-					'_' => 'Custom date/time format',	// TODO
-					'help' => 'Optional. A format supported by <a href="https://php.net/datetime.createfromformat" target="_blank"><code>DateTime::createFromFormat()</code></a> such as <code>d-m-Y H:i:s</code>',	// TODO
+					'_' => '自定义日期、时间格式',
+					'help' => '可选。一个被 <a href="https://php.net/datetime.createfromformat" target="_blank"><code>DateTime::createFromFormat()</code></a> 支持的日期、时间格式，例如 <code>d-m-Y H:i:s</code>',
 				),
 				'item_timestamp' => array(
 					'_' => '文章日期：',