diff --git a/composer.json b/composer.json
index fed4a61c843aad9ad703ff198cbd2da636298dc7..b598e7b8b3e35e06c90d7852f06a444e294ca9c2 100644
--- a/composer.json
+++ b/composer.json
@@ -8,7 +8,7 @@
         "wikimedia/composer-merge-plugin": "~1.3"
     },
     "replace": {
-        "drupal/core": "~8.3"
+        "drupal/core": "~8.4"
     },
     "minimum-stability": "dev",
     "prefer-stable": true,
diff --git a/composer.lock b/composer.lock
index e5406437b7c96aa36c6d272ee2848330472d9d53..486675c9cdf9acd544f9d00a70b770933e04f8ef 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,8 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "1167766f8eca494239cc8a1baa1ea6bb",
-    "content-hash": "0cfc95231ad5eb3f8d306e45c9cc92d9",
+    "content-hash": "324eae1731d25ba58e17ce0c32be7d02",
     "packages": [
         {
             "name": "asm89/stack-cors",
@@ -48,7 +47,7 @@
                 "cors",
                 "stack"
             ],
-            "time": "2016-08-01 12:05:04"
+            "time": "2016-08-01T12:05:04+00:00"
         },
         {
             "name": "composer/installers",
@@ -143,7 +142,7 @@
                 "zend",
                 "zikula"
             ],
-            "time": "2015-02-18 17:17:01"
+            "time": "2015-02-18T17:17:01+00:00"
         },
         {
             "name": "composer/semver",
@@ -204,7 +203,7 @@
                 "validation",
                 "versioning"
             ],
-            "time": "2015-09-21 09:42:36"
+            "time": "2015-09-21T09:42:36+00:00"
         },
         {
             "name": "doctrine/annotations",
@@ -272,7 +271,7 @@
                 "docblock",
                 "parser"
             ],
-            "time": "2015-08-31 12:32:49"
+            "time": "2015-08-31T12:32:49+00:00"
         },
         {
             "name": "doctrine/cache",
@@ -342,7 +341,7 @@
                 "cache",
                 "caching"
             ],
-            "time": "2015-08-31 12:36:41"
+            "time": "2015-08-31T12:36:41+00:00"
         },
         {
             "name": "doctrine/collections",
@@ -408,7 +407,7 @@
                 "collections",
                 "iterator"
             ],
-            "time": "2015-04-14 22:21:58"
+            "time": "2015-04-14T22:21:58+00:00"
         },
         {
             "name": "doctrine/common",
@@ -481,7 +480,7 @@
                 "persistence",
                 "spl"
             ],
-            "time": "2015-08-31 13:00:22"
+            "time": "2015-08-31T13:00:22+00:00"
         },
         {
             "name": "doctrine/inflector",
@@ -548,7 +547,7 @@
                 "singularize",
                 "string"
             ],
-            "time": "2014-12-20 21:24:13"
+            "time": "2014-12-20T21:24:13+00:00"
         },
         {
             "name": "doctrine/lexer",
@@ -602,7 +601,7 @@
                 "lexer",
                 "parser"
             ],
-            "time": "2014-09-09 13:34:57"
+            "time": "2014-09-09T13:34:57+00:00"
         },
         {
             "name": "easyrdf/easyrdf",
@@ -664,7 +663,7 @@
                 "rdfa",
                 "sparql"
             ],
-            "time": "2015-02-27 09:45:49"
+            "time": "2015-02-27T09:45:49+00:00"
         },
         {
             "name": "egulias/email-validator",
@@ -717,7 +716,7 @@
                 "validation",
                 "validator"
             ],
-            "time": "2015-06-22 21:07:51"
+            "time": "2015-06-22T21:07:51+00:00"
         },
         {
             "name": "guzzlehttp/guzzle",
@@ -779,7 +778,7 @@
                 "rest",
                 "web service"
             ],
-            "time": "2016-07-15 17:22:37"
+            "time": "2016-07-15T17:22:37+00:00"
         },
         {
             "name": "guzzlehttp/promises",
@@ -830,7 +829,7 @@
             "keywords": [
                 "promise"
             ],
-            "time": "2016-05-18 16:56:05"
+            "time": "2016-05-18T16:56:05+00:00"
         },
         {
             "name": "guzzlehttp/psr7",
@@ -888,7 +887,7 @@
                 "stream",
                 "uri"
             ],
-            "time": "2016-06-24 23:00:38"
+            "time": "2016-06-24T23:00:38+00:00"
         },
         {
             "name": "ircmaxell/password-compat",
@@ -930,7 +929,7 @@
                 "hashing",
                 "password"
             ],
-            "time": "2014-11-20 16:49:30"
+            "time": "2014-11-20T16:49:30+00:00"
         },
         {
             "name": "masterminds/html5",
@@ -995,7 +994,7 @@
                 "serializer",
                 "xml"
             ],
-            "time": "2016-05-10 14:11:45"
+            "time": "2016-05-10T14:11:45+00:00"
         },
         {
             "name": "paragonie/random_compat",
@@ -1043,7 +1042,7 @@
                 "pseudorandom",
                 "random"
             ],
-            "time": "2016-04-03 06:00:07"
+            "time": "2016-04-03T06:00:07+00:00"
         },
         {
             "name": "psr/http-message",
@@ -1092,7 +1091,7 @@
                 "request",
                 "response"
             ],
-            "time": "2015-05-04 20:22:00"
+            "time": "2015-05-04T20:22:00+00:00"
         },
         {
             "name": "psr/log",
@@ -1130,7 +1129,7 @@
                 "psr",
                 "psr-3"
             ],
-            "time": "2012-12-21 11:40:51"
+            "time": "2012-12-21T11:40:51+00:00"
         },
         {
             "name": "stack/builder",
@@ -1179,7 +1178,7 @@
             "keywords": [
                 "stack"
             ],
-            "time": "2016-06-02 06:58:42"
+            "time": "2016-06-02T06:58:42+00:00"
         },
         {
             "name": "symfony-cmf/routing",
@@ -1238,7 +1237,7 @@
                 "database",
                 "routing"
             ],
-            "time": "2016-03-31 09:11:39"
+            "time": "2016-03-31T09:11:39+00:00"
         },
         {
             "name": "symfony/class-loader",
@@ -1291,7 +1290,7 @@
             ],
             "description": "Symfony ClassLoader Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-10 14:03:07"
+            "time": "2017-01-10T14:03:07+00:00"
         },
         {
             "name": "symfony/console",
@@ -1352,7 +1351,7 @@
             ],
             "description": "Symfony Console Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-08 20:43:03"
+            "time": "2017-01-08T20:43:03+00:00"
         },
         {
             "name": "symfony/debug",
@@ -1409,7 +1408,7 @@
             ],
             "description": "Symfony Debug Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/dependency-injection",
@@ -1472,7 +1471,7 @@
             ],
             "description": "Symfony DependencyInjection Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-10 14:27:01"
+            "time": "2017-01-10T14:27:01+00:00"
         },
         {
             "name": "symfony/dom-crawler",
@@ -1528,7 +1527,7 @@
             ],
             "description": "Symfony DomCrawler Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/event-dispatcher",
@@ -1588,7 +1587,7 @@
             ],
             "description": "Symfony EventDispatcher Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/http-foundation",
@@ -1643,7 +1642,7 @@
             ],
             "description": "Symfony HttpFoundation Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-08 20:43:03"
+            "time": "2017-01-08T20:43:03+00:00"
         },
         {
             "name": "symfony/http-kernel",
@@ -1725,7 +1724,7 @@
             ],
             "description": "Symfony HttpKernel Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-12 20:27:24"
+            "time": "2017-01-12T20:27:24+00:00"
         },
         {
             "name": "symfony/polyfill-apcu",
@@ -1778,7 +1777,7 @@
                 "portable",
                 "shim"
             ],
-            "time": "2016-11-14 01:06:16"
+            "time": "2016-11-14T01:06:16+00:00"
         },
         {
             "name": "symfony/polyfill-iconv",
@@ -1837,7 +1836,7 @@
                 "portable",
                 "shim"
             ],
-            "time": "2016-11-14 01:06:16"
+            "time": "2016-11-14T01:06:16+00:00"
         },
         {
             "name": "symfony/polyfill-mbstring",
@@ -1896,7 +1895,7 @@
                 "portable",
                 "shim"
             ],
-            "time": "2016-11-14 01:06:16"
+            "time": "2016-11-14T01:06:16+00:00"
         },
         {
             "name": "symfony/polyfill-php54",
@@ -1954,7 +1953,7 @@
                 "portable",
                 "shim"
             ],
-            "time": "2016-11-14 01:06:16"
+            "time": "2016-11-14T01:06:16+00:00"
         },
         {
             "name": "symfony/polyfill-php55",
@@ -2010,7 +2009,7 @@
                 "portable",
                 "shim"
             ],
-            "time": "2016-11-14 01:06:16"
+            "time": "2016-11-14T01:06:16+00:00"
         },
         {
             "name": "symfony/process",
@@ -2059,7 +2058,7 @@
             ],
             "description": "Symfony Process Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/psr-http-message-bridge",
@@ -2113,7 +2112,7 @@
                 "http-message",
                 "psr-7"
             ],
-            "time": "2015-05-29 17:57:12"
+            "time": "2015-05-29T17:57:12+00:00"
         },
         {
             "name": "symfony/routing",
@@ -2188,7 +2187,7 @@
                 "uri",
                 "url"
             ],
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/serializer",
@@ -2252,7 +2251,7 @@
             ],
             "description": "Symfony Serializer Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/translation",
@@ -2316,7 +2315,7 @@
             ],
             "description": "Symfony Translation Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/validator",
@@ -2389,7 +2388,7 @@
             ],
             "description": "Symfony Validator Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-12 19:24:25"
+            "time": "2017-01-12T19:24:25+00:00"
         },
         {
             "name": "symfony/yaml",
@@ -2438,7 +2437,7 @@
             ],
             "description": "Symfony Yaml Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-03 13:49:52"
+            "time": "2017-01-03T13:49:52+00:00"
         },
         {
             "name": "twig/twig",
@@ -2499,7 +2498,7 @@
             "keywords": [
                 "templating"
             ],
-            "time": "2016-09-21 23:05:12"
+            "time": "2016-09-21T23:05:12+00:00"
         },
         {
             "name": "wikimedia/composer-merge-plugin",
@@ -2548,7 +2547,7 @@
                 }
             ],
             "description": "Composer plugin to merge multiple composer.json files",
-            "time": "2016-03-08 17:11:37"
+            "time": "2016-03-08T17:11:37+00:00"
         },
         {
             "name": "zendframework/zend-diactoros",
@@ -2598,7 +2597,7 @@
                 "psr",
                 "psr-7"
             ],
-            "time": "2015-08-10 20:04:20"
+            "time": "2015-08-10T20:04:20+00:00"
         },
         {
             "name": "zendframework/zend-escaper",
@@ -2642,7 +2641,7 @@
                 "escaper",
                 "zf2"
             ],
-            "time": "2015-06-03 14:05:37"
+            "time": "2015-06-03T14:05:37+00:00"
         },
         {
             "name": "zendframework/zend-feed",
@@ -2701,7 +2700,7 @@
                 "feed",
                 "zf2"
             ],
-            "time": "2015-08-04 21:39:18"
+            "time": "2015-08-04T21:39:18+00:00"
         },
         {
             "name": "zendframework/zend-hydrator",
@@ -2757,7 +2756,7 @@
                 "hydrator",
                 "zf2"
             ],
-            "time": "2015-09-17 14:06:43"
+            "time": "2015-09-17T14:06:43+00:00"
         },
         {
             "name": "zendframework/zend-stdlib",
@@ -2815,7 +2814,7 @@
                 "stdlib",
                 "zf2"
             ],
-            "time": "2015-09-25 04:06:33"
+            "time": "2015-09-25T04:06:33+00:00"
         }
     ],
     "packages-dev": [
@@ -2875,7 +2874,7 @@
                 "testing",
                 "web"
             ],
-            "time": "2016-10-17 08:31:38"
+            "time": "2016-10-17T08:31:38+00:00"
         },
         {
             "name": "behat/mink-browserkit-driver",
@@ -2931,7 +2930,7 @@
                 "browser",
                 "testing"
             ],
-            "time": "2016-03-05 08:59:47"
+            "time": "2016-03-05T08:59:47+00:00"
         },
         {
             "name": "behat/mink-goutte-driver",
@@ -2986,7 +2985,7 @@
                 "headless",
                 "testing"
             ],
-            "time": "2016-03-05 09:04:22"
+            "time": "2016-03-05T09:04:22+00:00"
         },
         {
             "name": "doctrine/instantiator",
@@ -3040,7 +3039,7 @@
                 "constructor",
                 "instantiate"
             ],
-            "time": "2015-06-14 21:17:01"
+            "time": "2015-06-14T21:17:01+00:00"
         },
         {
             "name": "fabpot/goutte",
@@ -3089,7 +3088,7 @@
             "keywords": [
                 "scraper"
             ],
-            "time": "2015-11-05 12:58:44"
+            "time": "2015-11-05T12:58:44+00:00"
         },
         {
             "name": "jcalderonzumba/gastonjs",
@@ -3146,7 +3145,7 @@
                 "headless",
                 "phantomjs"
             ],
-            "time": "2016-01-18 09:21:03"
+            "time": "2016-01-18T09:21:03+00:00"
         },
         {
             "name": "jcalderonzumba/mink-phantomjs-driver",
@@ -3207,7 +3206,7 @@
                 "phantomjs",
                 "testing"
             ],
-            "time": "2015-12-04 13:55:02"
+            "time": "2015-12-04T13:55:02+00:00"
         },
         {
             "name": "mikey179/vfsStream",
@@ -3253,7 +3252,7 @@
             ],
             "description": "Virtual file system to mock the real file system in unit tests.",
             "homepage": "http://vfs.bovigo.org/",
-            "time": "2015-10-06 16:59:57"
+            "time": "2015-10-06T16:59:57+00:00"
         },
         {
             "name": "phpdocumentor/reflection-docblock",
@@ -3302,7 +3301,7 @@
                     "email": "mike.vanriel@naenius.com"
                 }
             ],
-            "time": "2015-02-03 12:10:50"
+            "time": "2015-02-03T12:10:50+00:00"
         },
         {
             "name": "phpspec/prophecy",
@@ -3362,7 +3361,7 @@
                 "spy",
                 "stub"
             ],
-            "time": "2015-08-13 10:07:40"
+            "time": "2015-08-13T10:07:40+00:00"
         },
         {
             "name": "phpunit/php-code-coverage",
@@ -3424,7 +3423,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2015-10-06 15:47:00"
+            "time": "2015-10-06T15:47:00+00:00"
         },
         {
             "name": "phpunit/php-file-iterator",
@@ -3471,7 +3470,7 @@
                 "filesystem",
                 "iterator"
             ],
-            "time": "2015-06-21 13:08:43"
+            "time": "2015-06-21T13:08:43+00:00"
         },
         {
             "name": "phpunit/php-text-template",
@@ -3512,7 +3511,7 @@
             "keywords": [
                 "template"
             ],
-            "time": "2015-06-21 13:50:34"
+            "time": "2015-06-21T13:50:34+00:00"
         },
         {
             "name": "phpunit/php-timer",
@@ -3553,7 +3552,7 @@
             "keywords": [
                 "timer"
             ],
-            "time": "2015-06-21 08:01:12"
+            "time": "2015-06-21T08:01:12+00:00"
         },
         {
             "name": "phpunit/php-token-stream",
@@ -3602,7 +3601,7 @@
             "keywords": [
                 "tokenizer"
             ],
-            "time": "2015-09-15 10:49:45"
+            "time": "2015-09-15T10:49:45+00:00"
         },
         {
             "name": "phpunit/phpunit",
@@ -3674,7 +3673,7 @@
                 "testing",
                 "xunit"
             ],
-            "time": "2016-07-21 06:48:14"
+            "time": "2016-07-21T06:48:14+00:00"
         },
         {
             "name": "phpunit/phpunit-mock-objects",
@@ -3730,7 +3729,7 @@
                 "mock",
                 "xunit"
             ],
-            "time": "2015-10-02 06:51:40"
+            "time": "2015-10-02T06:51:40+00:00"
         },
         {
             "name": "sebastian/comparator",
@@ -3794,7 +3793,7 @@
                 "compare",
                 "equality"
             ],
-            "time": "2015-07-26 15:48:44"
+            "time": "2015-07-26T15:48:44+00:00"
         },
         {
             "name": "sebastian/diff",
@@ -3846,7 +3845,7 @@
             "keywords": [
                 "diff"
             ],
-            "time": "2015-02-22 15:13:53"
+            "time": "2015-02-22T15:13:53+00:00"
         },
         {
             "name": "sebastian/environment",
@@ -3896,7 +3895,7 @@
                 "environment",
                 "hhvm"
             ],
-            "time": "2015-08-03 06:14:51"
+            "time": "2015-08-03T06:14:51+00:00"
         },
         {
             "name": "sebastian/exporter",
@@ -3962,7 +3961,7 @@
                 "export",
                 "exporter"
             ],
-            "time": "2015-06-21 07:55:53"
+            "time": "2015-06-21T07:55:53+00:00"
         },
         {
             "name": "sebastian/global-state",
@@ -4013,7 +4012,7 @@
             "keywords": [
                 "global state"
             ],
-            "time": "2014-10-06 09:23:50"
+            "time": "2014-10-06T09:23:50+00:00"
         },
         {
             "name": "sebastian/recursion-context",
@@ -4066,7 +4065,7 @@
             ],
             "description": "Provides functionality to recursively process PHP variables",
             "homepage": "http://www.github.com/sebastianbergmann/recursion-context",
-            "time": "2015-06-21 08:04:50"
+            "time": "2015-06-21T08:04:50+00:00"
         },
         {
             "name": "sebastian/version",
@@ -4101,7 +4100,7 @@
             ],
             "description": "Library that helps with managing the version number of Git-hosted PHP projects",
             "homepage": "https://github.com/sebastianbergmann/version",
-            "time": "2015-06-21 13:59:46"
+            "time": "2015-06-21T13:59:46+00:00"
         },
         {
             "name": "symfony/browser-kit",
@@ -4158,7 +4157,7 @@
             ],
             "description": "Symfony BrowserKit Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         },
         {
             "name": "symfony/css-selector",
@@ -4211,7 +4210,7 @@
             ],
             "description": "Symfony CssSelector Component",
             "homepage": "https://symfony.com",
-            "time": "2017-01-02 20:30:24"
+            "time": "2017-01-02T20:30:24+00:00"
         }
     ],
     "aliases": [],
diff --git a/core/lib/Drupal.php b/core/lib/Drupal.php
index 4d3ea4e17d3d73c2503fc7719c1904385b3906de..b301cd97763e221c4f93492c149e46a860463073 100644
--- a/core/lib/Drupal.php
+++ b/core/lib/Drupal.php
@@ -81,7 +81,7 @@ class Drupal {
   /**
    * The current system version.
    */
-  const VERSION = '8.3.0-dev';
+  const VERSION = '8.4.0-dev';
 
   /**
    * Core API compatibility.