diff --git a/composer.json b/composer.json
index e342834a..3da7c4c7 100644
--- a/composer.json
+++ b/composer.json
@@ -11,7 +11,6 @@
         "ext-bcmath": "*",
         "ext-mbstring": "*",
         "twig/twig": "~2.4",
-        "nesbot/carbon": "~1.22",
         "swiftmailer/swiftmailer": "~6.0",
         "erusev/parsedown": "~1.6",
         "geoip2/geoip2": "~2.0",
diff --git a/composer.lock b/composer.lock
index 25e1a71f..85dce947 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "8d8235975900b7eff2b22be94207cfe1",
+    "content-hash": "eecb2be3db098c1aae02a69d52791f7d",
     "packages": [
         {
             "name": "composer/ca-bundle",
@@ -118,16 +118,16 @@
         },
         {
             "name": "egulias/email-validator",
-            "version": "2.1.5",
+            "version": "2.1.6",
             "source": {
                 "type": "git",
                 "url": "https://github.com/egulias/EmailValidator.git",
-                "reference": "54859fabea8b3beecbb1a282888d5c990036b9e3"
+                "reference": "0578b32b30b22de3e8664f797cf846fc9246f786"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/egulias/EmailValidator/zipball/54859fabea8b3beecbb1a282888d5c990036b9e3",
-                "reference": "54859fabea8b3beecbb1a282888d5c990036b9e3",
+                "url": "https://api.github.com/repos/egulias/EmailValidator/zipball/0578b32b30b22de3e8664f797cf846fc9246f786",
+                "reference": "0578b32b30b22de3e8664f797cf846fc9246f786",
                 "shasum": ""
             },
             "require": {
@@ -171,7 +171,7 @@
                 "validation",
                 "validator"
             ],
-            "time": "2018-08-16T20:49:45+00:00"
+            "time": "2018-09-25T20:47:26+00:00"
         },
         {
             "name": "erusev/parsedown",
@@ -434,61 +434,6 @@
             "homepage": "https://github.com/maxmind/web-service-common-php",
             "time": "2018-02-12T22:31:54+00:00"
         },
-        {
-            "name": "nesbot/carbon",
-            "version": "1.33.0",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/briannesbitt/Carbon.git",
-                "reference": "55667c1007a99e82030874b1bb14d24d07108413"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/briannesbitt/Carbon/zipball/55667c1007a99e82030874b1bb14d24d07108413",
-                "reference": "55667c1007a99e82030874b1bb14d24d07108413",
-                "shasum": ""
-            },
-            "require": {
-                "php": ">=5.3.9",
-                "symfony/translation": "~2.6 || ~3.0 || ~4.0"
-            },
-            "require-dev": {
-                "friendsofphp/php-cs-fixer": "~2",
-                "phpunit/phpunit": "^4.8.35 || ^5.7"
-            },
-            "type": "library",
-            "extra": {
-                "laravel": {
-                    "providers": [
-                        "Carbon\\Laravel\\ServiceProvider"
-                    ]
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "": "src/"
-                }
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Brian Nesbitt",
-                    "email": "brian@nesbot.com",
-                    "homepage": "http://nesbot.com"
-                }
-            ],
-            "description": "A simple API extension for DateTime.",
-            "homepage": "http://carbon.nesbot.com",
-            "keywords": [
-                "date",
-                "datetime",
-                "time"
-            ],
-            "time": "2018-08-07T08:39:47+00:00"
-        },
         {
             "name": "psr/log",
             "version": "1.0.2",
@@ -712,75 +657,6 @@
             ],
             "time": "2018-08-06T14:22:27+00:00"
         },
-        {
-            "name": "symfony/translation",
-            "version": "v4.1.4",
-            "source": {
-                "type": "git",
-                "url": "https://github.com/symfony/translation.git",
-                "reference": "fa2182669f7983b7aa5f1a770d053f79f0ef144f"
-            },
-            "dist": {
-                "type": "zip",
-                "url": "https://api.github.com/repos/symfony/translation/zipball/fa2182669f7983b7aa5f1a770d053f79f0ef144f",
-                "reference": "fa2182669f7983b7aa5f1a770d053f79f0ef144f",
-                "shasum": ""
-            },
-            "require": {
-                "php": "^7.1.3",
-                "symfony/polyfill-mbstring": "~1.0"
-            },
-            "conflict": {
-                "symfony/config": "<3.4",
-                "symfony/dependency-injection": "<3.4",
-                "symfony/yaml": "<3.4"
-            },
-            "require-dev": {
-                "psr/log": "~1.0",
-                "symfony/config": "~3.4|~4.0",
-                "symfony/console": "~3.4|~4.0",
-                "symfony/dependency-injection": "~3.4|~4.0",
-                "symfony/finder": "~2.8|~3.0|~4.0",
-                "symfony/intl": "~3.4|~4.0",
-                "symfony/yaml": "~3.4|~4.0"
-            },
-            "suggest": {
-                "psr/log-implementation": "To use logging capability in translator",
-                "symfony/config": "",
-                "symfony/yaml": ""
-            },
-            "type": "library",
-            "extra": {
-                "branch-alias": {
-                    "dev-master": "4.1-dev"
-                }
-            },
-            "autoload": {
-                "psr-4": {
-                    "Symfony\\Component\\Translation\\": ""
-                },
-                "exclude-from-classmap": [
-                    "/Tests/"
-                ]
-            },
-            "notification-url": "https://packagist.org/downloads/",
-            "license": [
-                "MIT"
-            ],
-            "authors": [
-                {
-                    "name": "Fabien Potencier",
-                    "email": "fabien@symfony.com"
-                },
-                {
-                    "name": "Symfony Community",
-                    "homepage": "https://symfony.com/contributors"
-                }
-            ],
-            "description": "Symfony Translation Component",
-            "homepage": "https://symfony.com",
-            "time": "2018-08-07T12:45:11+00:00"
-        },
         {
             "name": "twig/extensions",
             "version": "v1.5.2",
diff --git a/public/auth.php b/public/auth.php
index 7598c93c..1d40ebb5 100644
--- a/public/auth.php
+++ b/public/auth.php
@@ -1,5 +1,4 @@
 <?php
-use Carbon\Carbon;
 use Misuzu\Application;
 use Misuzu\Database;
 
@@ -315,7 +314,7 @@ MSG;
             }
 
             user_session_start($userId, $sessionKey);
-            $cookieLife = Carbon::now()->addMonth()->timestamp;
+            $cookieLife = strtotime(user_session_current('expires_on'));
             set_cookie_m('uid', $userId, $cookieLife);
             set_cookie_m('sid', $sessionKey, $cookieLife);
 
diff --git a/src/Application.php b/src/Application.php
index 39b1c48d..d7323692 100644
--- a/src/Application.php
+++ b/src/Application.php
@@ -1,7 +1,6 @@
 <?php
 namespace Misuzu;
 
-use Carbon\Carbon;
 use UnexpectedValueException;
 use InvalidArgumentException;
 use Swift_Mailer;