diff --git a/lib/default.php b/lib/default.php
index 4f3ea00f2a..bb7708bfcd 100644
--- a/lib/default.php
+++ b/lib/default.php
@@ -175,7 +175,7 @@ $default =
         array('enabled' => false),
         'integration' =>
         array('source' => 'StatusNet', # source attribute for Twitter
-              'taguri' => $_server.',2009'), # base for tag URIs
+              'taguri' => null), # base for tag URIs
         'twitter' =>
         array('enabled'       => true,
               'consumer_key'    => null,
diff --git a/lib/taguri.php b/lib/taguri.php
new file mode 100644
index 0000000000..d8398eded5
--- /dev/null
+++ b/lib/taguri.php
@@ -0,0 +1,96 @@
+<?php
+/**
+ * StatusNet, the distributed open-source microblogging tool
+ *
+ * Utility for creating new tag: URIs
+ *
+ * PHP version 5
+ *
+ * LICENCE: This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  URI
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2010 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPLv3
+ * @link      http://status.net/
+ */
+
+if (!defined('STATUSNET')) {
+    exit(1);
+}
+
+/**
+ * Mint tag: URIs
+ *
+ * tag: URIs are unique identifiers according to http://tools.ietf.org/html/rfc4151.
+ *
+ * We use them for creating URIs for things that can't be HTTP retrieved.
+ *
+ * @category URI
+ * @package  StatusNet
+ * @author   Evan Prodromou <evan@status.net>
+ * @license  http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPLv3
+ * @link     http://status.net/
+ */
+
+class TagURI
+{
+    /**
+     * Return the base part of a tag URI
+     *
+     * Note: use mint() instead.
+     *
+     * @return string Tag URI base to use
+     */
+
+    static function base()
+    {
+        $base = common_config('integration', 'taguri');
+
+        if (empty($base)) {
+
+            $base = common_config('site', 'server').','.date('Y-m-d');
+
+            $pathPart = trim(common_config('site', 'path'), '/');
+
+            if (!empty($pathPart)) {
+                $base .= ':'.str_replace('/', ':', $pathPart);
+            }
+        }
+
+        return $base;
+    }
+
+    /**
+     * Make a new tag URI
+     *
+     * Builds the proper base and creates all the parts
+     *
+     * @return string minted URI
+     */
+
+    static function mint()
+    {
+        $base = self::base();
+
+        $args = func_get_args();
+
+        $format = array_shift($args);
+
+        $extra = vsprintf($format, $args);
+
+        return 'tag:'.$base.':'.$extra;
+    }
+}
diff --git a/tests/TagURITest.php b/tests/TagURITest.php
new file mode 100644
index 0000000000..d23f8bfe66
--- /dev/null
+++ b/tests/TagURITest.php
@@ -0,0 +1,36 @@
+<?php
+
+if (isset($_SERVER) && array_key_exists('REQUEST_METHOD', $_SERVER)) {
+    print "This script must be run from the command line\n";
+    exit();
+}
+
+define('INSTALLDIR', realpath(dirname(__FILE__) . '/..'));
+define('STATUSNET', true);
+
+require_once INSTALLDIR . '/lib/common.php';
+
+$config['site']['server'] = 'example.net';
+$config['site']['path']   = '/apps/statusnet';
+
+class TagURITest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @dataProvider provider
+     */
+    public function testProduction($format, $args, $uri)
+    {
+        $minted = call_user_func_array(array('TagURI', 'mint'),
+                                       array_merge(array($format), $args));
+
+        $this->assertEquals($uri, $minted);
+    }
+
+    static public function provider()
+    {
+        return array(array('favorite:%d:%d',
+                           array(1, 3),
+                           'tag:example.net,'.date('Y-m-d').':apps:statusnet:favorite:1:3'));
+    }
+}
+