diff --git a/src/Gateways/AliyunGateway.php b/src/Gateways/AliyunGateway.php
index 8b442bb..178dfe8 100644
--- a/src/Gateways/AliyunGateway.php
+++ b/src/Gateways/AliyunGateway.php
@@ -66,7 +66,7 @@ public function send(PhoneNumberInterface $to, MessageInterface $message, Config
             'SignatureMethod' => self::ENDPOINT_SIGNATURE_METHOD,
             'SignatureVersion' => self::ENDPOINT_SIGNATURE_VERSION,
             'SignatureNonce' => uniqid(),
-            'Timestamp' => $this->getTimestamp(),
+            'Timestamp' => gmdate('Y-m-d\TH:i:s\Z'),
             'Action' => self::ENDPOINT_METHOD,
             'Version' => self::ENDPOINT_VERSION,
             'PhoneNumbers' => !\is_null($to->getIDDCode()) ? strval($to->getZeroPrefixedNumber()) : $to->getNumber(),
@@ -101,17 +101,4 @@ protected function generateSign($params)
 
         return base64_encode(hash_hmac('sha1', $stringToSign, $accessKeySecret.'&', true));
     }
-
-    /**
-     * @return false|string
-     */
-    protected function getTimestamp()
-    {
-        $timezone = date_default_timezone_get();
-        date_default_timezone_set('GMT');
-        $timestamp = date('Y-m-d\TH:i:s\Z');
-        date_default_timezone_set($timezone);
-
-        return $timestamp;
-    }
 }
diff --git a/src/Gateways/BaiduGateway.php b/src/Gateways/BaiduGateway.php
index 0d34c72..cc23c41 100644
--- a/src/Gateways/BaiduGateway.php
+++ b/src/Gateways/BaiduGateway.php
@@ -56,7 +56,7 @@ public function send(PhoneNumberInterface $to, MessageInterface $message, Config
             'contentVar' => $message->getData($this),
         ];
 
-        $datetime = date('Y-m-d\TH:i:s\Z');
+        $datetime = gmdate('Y-m-d\TH:i:s\Z');
 
         $headers = [
             'host' => self::ENDPOINT_HOST,