diff --git a/composer.json b/composer.json
index fc6ad33..08f960c 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,8 @@
     "abraham/twitteroauth": "*",
     "andreyco/instagram": "3.*",
     "p3k/multipart": "*",
-    "tantek/cassis": "*"
+    "tantek/cassis": "*",
+    "p3k/timezone": "*"
   },
   "autoload": {
     "files": [
diff --git a/composer.lock b/composer.lock
index 169e3ff..ec0f1ff 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": "4756e7ef0035b8f768f07d252adbdc17",
-    "content-hash": "f4709cc6bd166e3759fbedbfbaa7752e",
+    "content-hash": "4ec77b1fe4974da5d6a392ec0d362858",
     "packages": [
         {
             "name": "abraham/twitteroauth",
@@ -59,7 +58,7 @@
                 "social",
                 "twitter"
             ],
-            "time": "2016-12-12 17:42:13"
+            "time": "2016-12-12T17:42:13+00:00"
         },
         {
             "name": "andreyco/instagram",
@@ -102,7 +101,7 @@
                 "api",
                 "instagram"
             ],
-            "time": "2016-07-17 23:42:10"
+            "time": "2016-07-17T23:42:10+00:00"
         },
         {
             "name": "barnabywalters/mf-cleaner",
@@ -142,7 +141,7 @@
                 }
             ],
             "description": "Cleans up microformats2 array structures",
-            "time": "2014-10-06 23:11:15"
+            "time": "2014-10-06T23:11:15+00:00"
         },
         {
             "name": "firebase/php-jwt",
@@ -186,7 +185,7 @@
             ],
             "description": "A simple library to encode and decode JSON Web Tokens (JWT) in PHP. Should conform to the current spec.",
             "homepage": "https://github.com/firebase/php-jwt",
-            "time": "2015-06-22 23:26:39"
+            "time": "2015-06-22T23:26:39+00:00"
         },
         {
             "name": "indieauth/client",
@@ -225,7 +224,7 @@
                 }
             ],
             "description": "IndieAuth Client Library",
-            "time": "2016-02-08 23:56:31"
+            "time": "2016-02-08T23:56:31+00:00"
         },
         {
             "name": "indieweb/date-formatter",
@@ -268,7 +267,7 @@
                 "microformats",
                 "microformats2"
             ],
-            "time": "2015-10-28 00:32:39"
+            "time": "2015-10-28T00:32:39+00:00"
         },
         {
             "name": "indieweb/link-rel-parser",
@@ -314,7 +313,7 @@
                 "indieweb",
                 "microformats2"
             ],
-            "time": "2013-12-23 00:14:58"
+            "time": "2013-12-23T00:14:58+00:00"
         },
         {
             "name": "indieweb/mention-client",
@@ -353,7 +352,7 @@
             ],
             "description": "Client library for sending webmention and pingback notifications",
             "homepage": "https://github.com/indieweb/mention-client-php",
-            "time": "2015-04-03 11:21:06"
+            "time": "2015-04-03T11:21:06+00:00"
         },
         {
             "name": "j4mie/idiorm",
@@ -411,7 +410,7 @@
                 "orm",
                 "query builder"
             ],
-            "time": "2013-12-12 10:25:27"
+            "time": "2013-12-12T10:25:27+00:00"
         },
         {
             "name": "mf2/mf2",
@@ -464,7 +463,7 @@
                 "parser",
                 "semantic"
             ],
-            "time": "2015-07-12 14:10:01"
+            "time": "2015-07-12T14:10:01+00:00"
         },
         {
             "name": "mpratt/relativetime",
@@ -512,7 +511,7 @@
                 "time",
                 "time-ago"
             ],
-            "time": "2015-12-24 12:43:04"
+            "time": "2015-12-24T12:43:04+00:00"
         },
         {
             "name": "p3k/multipart",
@@ -548,7 +547,49 @@
                 }
             ],
             "description": "Multipart Encoding Library",
-            "time": "2015-07-16 19:28:02"
+            "time": "2015-07-16T19:28:02+00:00"
+        },
+        {
+            "name": "p3k/timezone",
+            "version": "0.1.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/aaronpk/p3k-timezone.git",
+                "reference": "68d3490d896f98cf0727dc937f0bb6b045050c83"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/aaronpk/p3k-timezone/zipball/68d3490d896f98cf0727dc937f0bb6b045050c83",
+                "reference": "68d3490d896f98cf0727dc937f0bb6b045050c83",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=5.4.0"
+            },
+            "type": "library",
+            "autoload": {
+                "files": [
+                    "src/p3k/Timezone.php"
+                ]
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "Apache-2.0"
+            ],
+            "authors": [
+                {
+                    "name": "Aaron Parecki",
+                    "homepage": "https://aaronparecki.com"
+                }
+            ],
+            "description": "Find the timezone of a given location",
+            "homepage": "https://github.com/aaronpk/p3k-timezone",
+            "keywords": [
+                "date",
+                "p3k",
+                "timezone"
+            ],
+            "time": "2017-01-12T17:30:08+00:00"
         },
         {
             "name": "saltybeagle/savant3",
@@ -626,7 +667,7 @@
                 "rest",
                 "router"
             ],
-            "time": "2012-12-13 02:15:50"
+            "time": "2012-12-13T02:15:50+00:00"
         },
         {
             "name": "tantek/cassis",
@@ -649,7 +690,7 @@
                 ]
             },
             "notification-url": "https://packagist.org/downloads/",
-            "time": "2016-04-04 15:31:04"
+            "time": "2016-04-04T15:31:04+00:00"
         }
     ],
     "packages-dev": [],
diff --git a/controllers/controllers.php b/controllers/controllers.php
index 4de4aee..505589f 100644
--- a/controllers/controllers.php
+++ b/controllers/controllers.php
@@ -213,6 +213,25 @@ $app->post('/prefs', function() use($app) {
   )));
 });
 
+$app->post('/prefs/timezone', function() use($app) {
+  // Called when the interface finds the user's location.
+  // Look up the timezone for this location and store it as their default.
+  $timezone = false;
+  if($user=require_login($app)) {
+    $params = $app->request()->params();
+    $timezone = p3k\Timezone::timezone_for_location($params['latitude'], $params['longitude']);
+    if($timezone) {
+      $user->default_timezone = $timezone;
+      $user->save();
+    }
+  }
+  $app->response()['Content-type'] = 'application/json';
+  $app->response()->body(json_encode(array(
+    'result' => 'ok',
+    'timezone' => $timezone,
+  )));
+});
+
 $app->get('/add-to-home', function() use($app) {
   $params = $app->request()->params();
   header("Cache-Control: no-cache, must-revalidate");
diff --git a/public/index.php b/public/index.php
index 0909780..bca3b43 100644
--- a/public/index.php
+++ b/public/index.php
@@ -13,6 +13,7 @@ $app = new \Slim\Slim(array(
 
 require 'controllers/auth.php';
 require 'controllers/controllers.php';
+require 'controllers/micropub.php';
 require 'controllers/static.php';
 require 'controllers/editor.php';
 require 'controllers/hooks.php';
diff --git a/schema/migrations/0003.sql b/schema/migrations/0003.sql
new file mode 100644
index 0000000..43b72f7
--- /dev/null
+++ b/schema/migrations/0003.sql
@@ -0,0 +1,2 @@
+ALTER TABLE users
+ADD COLUMN `default_timezone` VARCHAR(255);
diff --git a/schema/mysql.sql b/schema/mysql.sql
index 610b01b..31f10fd 100644
--- a/schema/mysql.sql
+++ b/schema/mysql.sql
@@ -21,6 +21,7 @@ CREATE TABLE `users` (
   `twitter_token_secret` text,
   `twitter_username` varchar(255) DEFAULT NULL,
   `instagram_access_token` text,
-  `email_username` varchar(255) DEFAULT NULL,
+  `email_username` vacrchar(255) DEFAULT NULL,
+  `default_timezone` vacrchar(255) DEFAULT NULL,
   PRIMARY KEY (`id`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
diff --git a/views/new-post.php b/views/new-post.php
index de56ddb..434f54e 100644
--- a/views/new-post.php
+++ b/views/new-post.php
@@ -532,6 +532,11 @@ $(function(){
       $("#note_location_img").show();
       $("#note_location_msg").addClass("img-visible");
 
+      $.post("/prefs/timezone", {
+        latitude: position.coords.latitude,
+        longitude: position.coords.longitude
+      });
+
     }, function(err){
       if(err.code == 1) {
         location_error("The website was not able to get permission");