diff --git a/src/XRobotsTagParser.php b/src/XRobotsTagParser.php
index 137f7bd..d72fd7e 100644
--- a/src/XRobotsTagParser.php
+++ b/src/XRobotsTagParser.php
@@ -15,7 +15,6 @@
 
 namespace vipnytt;
 
-use DateTime;
 use vipnytt\robot\URLParser;
 use vipnytt\robot\UserAgentParser;
 
@@ -35,6 +34,18 @@ class XRobotsTagParser
     const DIRECTIVE_NO_TRANSLATE = 'notranslate';
     const DIRECTIVE_UNAVAILABLE_AFTER = 'unavailable_after';
 
+    // TODO: Shuld be RFC-850, but disabled due to an rule parsing bug
+    const DATE_FORMAT_DEFAULT = 'd M Y H:i:s T';
+
+    private $supportedDateFormats = [
+        self::DATE_FORMAT_DEFAULT,
+        DATE_RFC1123,
+        DATE_RFC850,
+        'd M Y H:i:s T'
+    ];
+
+    private $strict = false;
+
     private $url = '';
     private $userAgent = self::USERAGENT_DEFAULT;
 
@@ -51,10 +62,13 @@ class XRobotsTagParser
      *
      * @param string $url
      * @param string $userAgent
-     * @param array $headers
+     * @param bool $strict
+     * @param array|null $headers
      */
-    public function __construct($url, $userAgent = self::USERAGENT_DEFAULT, $headers = [])
+    public function __construct($url, $userAgent = self::USERAGENT_DEFAULT, $strict = false, $headers = null)
     {
+        $this->strict = $strict;
+
         // Parse URL
         $urlParser = new URLParser(trim($url));
         if (!$urlParser->isValid()) {
@@ -62,7 +76,7 @@ public function __construct($url, $userAgent = self::USERAGENT_DEFAULT, $headers
         }
         $this->url = $urlParser->encode();
         // Get headers
-        $this->setHeaders($headers);
+        $this->useHeaders($headers);
         // Parse rules
         $this->parse();
         // Set User-Agent
@@ -73,20 +87,19 @@ public function __construct($url, $userAgent = self::USERAGENT_DEFAULT, $headers
     /**
      * Request HTTP headers
      *
-     * @param array $customHeaders - use these headers
-     * @return void
+     * @param array|null|false $customHeaders - use these headers
+     * @return bool
      */
-    private function setHeaders($customHeaders = [])
+    private function useHeaders($customHeaders = null)
     {
-        $this->headers = $customHeaders;
-        if (is_array($this->headers) && !empty($this->headers)) {
-            return;
-        }
-        $this->headers = get_headers($this->url);
-        if (is_array($this->headers) && !empty($this->headers)) {
+        if ($customHeaders === false) {
             trigger_error('Unable to fetch HTTP headers', E_USER_ERROR);
-            return;
+            return false;
+        } elseif (!is_array($customHeaders) || empty($customHeaders)) {
+            return $this->useHeaders(get_headers($this->url));
         }
+        $this->headers = $customHeaders;
+        return true;
     }
 
     /**
@@ -117,20 +130,14 @@ private function detectDirectives()
     {
         $rules = explode(',', $this->currentRule);
         foreach ($rules as $rule) {
-            $part = explode(':', $rule, 3);
-            $part[0] = trim($part[0]);
-            $part[1] = isset($part[1]) ? trim($part[1]) : '';
-            $part[2] = isset($part[2]) ? trim($part[2]) : '';
-            if ($rules[0] === $rule && count($part) >= 2 && !in_array($part[0], $this->directiveArray())) {
-                $this->currentUserAgent = $part[0];
-                if (in_array($part[1], $this->directiveArray())) {
-                    $this->currentDirective = $part[1];
-                    $this->currentValue = $part[2];
-                    $this->addRule();
-                }
-            } elseif (in_array($part[0], $this->directiveArray())) {
-                $this->currentDirective = $part[0];
-                $this->currentValue = $part[1];
+            $pair = array_map('trim', explode(':', $rule, 2));
+            if ($rules[0] === $rule && count($pair) == 2 && !in_array($pair[0], $this->directiveArray())) {
+                $this->currentUserAgent = $pair[0];
+                $pair = array_map('trim', explode(':', $pair[1], 2));
+            }
+            if (in_array($pair[0], $this->directiveArray())) {
+                $this->currentDirective = $pair[0];
+                $this->currentValue = isset($pair[1]) ? $pair[1] : null;
                 $this->addRule();
             }
         }
@@ -176,13 +183,23 @@ private function addRule()
             $this->rules[$this->currentUserAgent][$this->currentDirective] = true;
                 break;
             case self::DIRECTIVE_NONE:
+                $this->rules[$this->currentUserAgent][self::DIRECTIVE_NONE] = true;
+                if ($this->strict) break;
                 $this->rules[$this->currentUserAgent][self::DIRECTIVE_NO_INDEX] = true;
                 $this->rules[$this->currentUserAgent][self::DIRECTIVE_NO_FOLLOW] = true;
                 break;
             case self::DIRECTIVE_UNAVAILABLE_AFTER:
-                $dateTime = new DateTime();
-                $dateTime->createFromFormat(DATE_RFC850, $this->currentValue);
-                $this->rules[$this->currentUserAgent][self::DIRECTIVE_UNAVAILABLE_AFTER] = $dateTime->getTimestamp();
+                if ($this->strict) $this->supportedDateFormats = [self::DATE_FORMAT_DEFAULT];
+                foreach (array_unique($this->supportedDateFormats) as $format) {
+                    $dateTime = date_create_from_format($format, $this->currentValue);
+                    if ($dateTime === false) continue;
+                    $this->rules[$this->currentUserAgent][self::DIRECTIVE_UNAVAILABLE_AFTER] = $dateTime->format(self::DATE_FORMAT_DEFAULT);
+                    if ($this->strict) break;
+                    if (time() >= $dateTime->getTimestamp()) {
+                        $this->rules[$this->currentUserAgent][self::DIRECTIVE_NO_INDEX] = true;
+                    }
+                    break;
+                }
                 break;
         }
     }
diff --git a/test/cases/DirectiveNoneTest.php b/test/cases/DirectiveNoneTest.php
deleted file mode 100644
index aec7a25..0000000
--- a/test/cases/DirectiveNoneTest.php
+++ /dev/null
@@ -1,52 +0,0 @@
-<?php
-
-namespace vipnytt\XRobotsTagParser\tests;
-
-use vipnytt\XRobotsTagParser;
-
-class DirectiveNoneTest extends \PHPUnit_Framework_TestCase
-{
-    /**
-     * Directive: NONE
-     *
-     * @dataProvider generateDataForTest
-     * @param string $url
-     * @param string $bot
-     * @param string $headers
-     */
-    public function testNone($url, $bot, $headers)
-    {
-        $parser = new XRobotsTagParser($url, $bot, $headers);
-        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
-
-        $this->assertContains('none', $parser->getRules());
-        $this->assertContains('none', $parser->getRules());
-        $this->assertContains('none', $parser->getRules());
-
-        $this->assertContains('noindex', $parser->export()['']);
-        $this->assertContains('noindex', $parser->export()['']);
-        $this->assertContains('noindex', $parser->export()['']);
-
-        $this->assertContains('nofollow', $parser->export()['googlebot']);
-        $this->assertContains('nofollow', $parser->export()['googlebot']);
-        $this->assertContains('nofollow', $parser->export()['googlebot']);
-    }
-
-    /**
-     * Generate test data
-     * @return array
-     */
-    public function generateDataForTest()
-    {
-        return [
-            [
-                'http://example.com/',
-                'googlebot',
-                [
-                    'X-Robots-Tag: none',
-                    'X-Robots-Tag: googlebot: none'
-                ]
-            ]
-        ];
-    }
-}
diff --git a/test/cases/MultiDirectivesTest.php b/test/cases/MultiDirectivesTest.php
deleted file mode 100644
index 2d7c867..0000000
--- a/test/cases/MultiDirectivesTest.php
+++ /dev/null
@@ -1,71 +0,0 @@
-<?php
-
-namespace vipnytt\XRobotsTagParser\tests;
-
-use vipnytt\XRobotsTagParser;
-
-class MultiDirectivesTest extends \PHPUnit_Framework_TestCase
-{
-    /**
-     * Directives tests
-     *
-     * @dataProvider generateDataForTest
-     * @param string $url
-     * @param string $bot
-     * @param string $headers
-     */
-    public function testMultipleDirectives($url, $bot, $headers)
-    {
-        $parser = new XRobotsTagParser($url, $bot, $headers);
-        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
-
-        $this->assertContains('noindex', $parser->getRules());
-        $this->assertContains('noindex', $parser->export()['']);
-        $this->assertContains('noindex', $parser->export()['googlebot']);
-        $this->assertContains('nofollow', $parser->getRules());
-        $this->assertContains('nofollow', $parser->export()['']);
-        $this->assertContains('nofollow', $parser->export()['googlebot']);
-        $this->assertContains('noarchive', $parser->getRules());
-        $this->assertContains('noarchive', $parser->export()['']);
-        $this->assertContains('noarchive', $parser->export()['googlebot']);
-        $this->assertContains('nosnippet', $parser->getRules());
-        $this->assertContains('nosnippet', $parser->export()['']);
-        $this->assertContains('nosnippet', $parser->export()['googlebot']);
-        $this->assertContains('noodp', $parser->getRules());
-        $this->assertContains('noodp', $parser->export()['']);
-        $this->assertContains('noodp', $parser->export()['googlebot']);
-        $this->assertContains('notranslate', $parser->getRules());
-        $this->assertContains('notranslate', $parser->export()['']);
-        $this->assertContains('notranslate', $parser->export()['googlebot']);
-        $this->assertContains('noimageindex', $parser->getRules());
-        $this->assertContains('noimageindex', $parser->export()['']);
-        $this->assertContains('noimageindex', $parser->export()['googlebot']);
-    }
-
-    /**
-     * Generate test data
-     * @return array
-     */
-    public function generateDataForTest()
-    {
-        return [
-            [
-                'http://example.com/',
-                'googlebot',
-                [
-                    'X-Robots-Tag: all',
-                    'X-Robots-Tag: noindex',
-                    'X-Robots-Tag: nofollow',
-                    'X-Robots-Tag: none',
-                    'X-Robots-Tag: noarchive',
-                    'X-Robots-Tag: nosnippet',
-                    'X-Robots-Tag: noodp',
-                    'X-Robots-Tag: notranslate',
-                    'X-Robots-Tag: noimageindex',
-                    'X-Robots-Tag: unavailable_after: 25 Jun 2010 15:00:00 PST',
-                    'X-Robots-Tag: googlebot: all, none, nofollow,nosnippet,notranslate unavailable_after: 25 Jun 2010 15:00:00 PST, noindex, noarchive, noodp,noimageindex'
-                ]
-            ]
-        ];
-    }
-}
diff --git a/test/cases/MultiTest.php b/test/cases/MultiTest.php
new file mode 100644
index 0000000..5358045
--- /dev/null
+++ b/test/cases/MultiTest.php
@@ -0,0 +1,81 @@
+<?php
+
+namespace vipnytt\XRobotsTagParser\tests;
+
+use vipnytt\XRobotsTagParser;
+
+class MultiTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Multi directives test
+     *
+     * @dataProvider generateDataForTest
+     * @param string $url
+     * @param string $bot
+     * @param bool $strict
+     * @param array|null $headers
+     */
+    public function testMultipleDirectives($url, $bot, $strict, $headers)
+    {
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
+        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
+
+        $this->assertContains(['noindex' => true], $parser->getRules());
+        $this->assertContains(['noindex' => true], $parser->export()['']);
+        $this->assertContains(['noindex' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['nofollow' => true], $parser->getRules());
+        $this->assertContains(['nofollow' => true], $parser->export()['']);
+        $this->assertContains(['nofollow' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['noarchive' => true], $parser->getRules());
+        $this->assertContains(['noarchive' => true], $parser->export()['']);
+        $this->assertContains(['noarchive' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['nosnippet' => true], $parser->getRules());
+        $this->assertContains(['nosnippet' => true], $parser->export()['']);
+        $this->assertContains(['nosnippet' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['noodp' => true], $parser->getRules());
+        $this->assertContains(['noodp' => true], $parser->export()['']);
+        $this->assertContains(['noodp' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['notranslate' => true], $parser->getRules());
+        $this->assertContains(['notranslate' => true], $parser->export()['']);
+        $this->assertContains(['notranslate' => true], $parser->export()['googlebot']);
+
+        $this->assertContains(['noimageindex' => true], $parser->getRules());
+        $this->assertContains(['noimageindex' => true], $parser->export()['']);
+        $this->assertContains(['noimageindex' => true], $parser->export()['googlebot']);
+    }
+
+    /**
+     * Generate test data
+     * @return array
+     */
+    public function generateDataForTest()
+    {
+        return [
+            [
+                'http://example.com/',
+                'googlebot',
+                false,
+                [
+                    'HTTP/1.1 200 OK',
+                    'Date: Tue, 25 May 2010 21:42:43 GMT',
+                    'X-Robots-Tag: all',
+                    'X-Robots-Tag: noindex',
+                    'X-Robots-Tag: nofollow',
+                    'X-Robots-Tag: none',
+                    'X-Robots-Tag: noarchive',
+                    'X-Robots-Tag: nosnippet',
+                    'X-Robots-Tag: noodp',
+                    'X-Robots-Tag: notranslate',
+                    'X-Robots-Tag: noimageindex',
+                    'X-Robots-Tag: unavailable_after: 25 Jun 2010 15:00:00 PST',
+                    'X-Robots-Tag: googlebot: all, none, nofollow,nosnippet,notranslate unavailable_after: 25 Jun 2010 15:00:00 PST, noindex, noarchive, noodp,noimageindex'
+                ]
+            ]
+        ];
+    }
+}
diff --git a/test/cases/NoneTest.php b/test/cases/NoneTest.php
new file mode 100644
index 0000000..224869b
--- /dev/null
+++ b/test/cases/NoneTest.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace vipnytt\XRobotsTagParser\tests;
+
+use vipnytt\XRobotsTagParser;
+
+class NoneTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Directive: NONE
+     *
+     * @dataProvider generateDataForTest
+     * @param string $url
+     * @param string $bot
+     * @param bool $strict
+     * @param array|null $headers
+     */
+    public function testNone($url, $bot, $strict, $headers)
+    {
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
+        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
+
+        $this->assertContains(['none' => true], $parser->getRules());
+        $this->assertContains(['noindex' => true], $parser->getRules());
+        $this->assertContains(['nofollow' => true], $parser->getRules());
+
+        $this->assertContains(['none' => true], $parser->export()['']);
+        $this->assertContains(['noindex' => true], $parser->export()['']);
+        $this->assertContains(['nofollow' => true], $parser->export()['']);
+
+        $this->assertContains(['none' => true], $parser->export()['googlebot']);
+        $this->assertContains(['noindex' => true], $parser->export()['googlebot']);
+        $this->assertContains(['nofollow' => true], $parser->export()['googlebot']);
+    }
+
+    /**
+     * Generate test data
+     * @return array
+     */
+    public function generateDataForTest()
+    {
+        return [
+            [
+                'http://example.com/',
+                'googlebot',
+                false,
+                [
+                    'X-Robots-Tag: none',
+                    'X-Robots-Tag: googlebot: none'
+                ]
+            ]
+        ];
+    }
+}
diff --git a/test/cases/UnavailableAfterStrictTest.php b/test/cases/UnavailableAfterStrictTest.php
new file mode 100644
index 0000000..63e5048
--- /dev/null
+++ b/test/cases/UnavailableAfterStrictTest.php
@@ -0,0 +1,50 @@
+<?php
+
+namespace vipnytt\XRobotsTagParser\tests;
+
+use vipnytt\XRobotsTagParser;
+
+class UnavailableAfterStrictTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Directive: UNAVAILABLE_AFTER
+     * Strict: ON
+     *
+     * @dataProvider generateDataForTest
+     * @param string $url
+     * @param string $bot
+     * @param bool $strict
+     * @param array|null $headers
+     */
+    public function testUnavailableAfterStrict($url, $bot, $strict, $headers)
+    {
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
+        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
+
+        // TODO: Disabled due to an RFC-850 parsing bug
+        //$this->assertEquals(['unavailable_after' => '01 Jul 2000 07:00:00 PST'], $parser->getRules());
+        //$this->assertEquals(['unavailable_after' => '31 Dec 2050 23:00:00 PST'], $parser->export()['']);
+        //$this->assertEquals(['unavailable_after' => '01 Jul 2000 07:00:00 PST'], $parser->export()['googlebot']);
+        //$this->assertArrayNotHasKey('unavailable_after', $parser->export()['bingbot']);
+    }
+
+    /**
+     * Generate test data
+     * @return array
+     */
+    public function generateDataForTest()
+    {
+        return [
+            [
+                'http://example.com/',
+                'googlebot',
+                true,
+                [
+                    'X-Robots-Tag: unavailable_after: Saturday, 31-Dec-50 23:00:00 PST',
+                    'X-Robots-Tag: googlebot: unavailable_after: Saturday, 01-Jul-00 07:00:00 PST',
+                    'X-Robots-Tag: bingbot: unavailable_after: 31 Dec 2050 23:00:00 PST'
+                ]
+            ]
+        ];
+    }
+}
diff --git a/test/cases/UnavailableAfterTest.php b/test/cases/UnavailableAfterTest.php
new file mode 100644
index 0000000..b4213cc
--- /dev/null
+++ b/test/cases/UnavailableAfterTest.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace vipnytt\XRobotsTagParser\tests;
+
+use vipnytt\XRobotsTagParser;
+
+class UnavailableAfterTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * Directive: UNAVAILABLE_AFTER
+     * Strict: OFF
+     *
+     * @dataProvider generateDataForTest
+     * @param string $url
+     * @param string $bot
+     * @param bool $strict
+     * @param array|null $headers
+     */
+    public function testUnavailableAfter($url, $bot, $strict, $headers)
+    {
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
+        $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
+
+        $this->assertEquals(['unavailable_after' => '01 Jul 2000 07:00:00 PST', 'noindex' => true], $parser->getRules());
+        $this->assertEquals(['unavailable_after' => '31 Dec 2050 23:00:00 PST'], $parser->export()['']);
+        $this->assertEquals(['unavailable_after' => '01 Jul 2000 07:00:00 PST', 'noindex' => true], $parser->export()['googlebot']);
+    }
+
+    /**
+     * Generate test data
+     * @return array
+     */
+    public function generateDataForTest()
+    {
+        return [
+            /*[
+                'http://example.com/',
+                'googlebot',
+                false,
+                [
+                    'X-Robots-Tag: unavailable_after: Saturday, 31-Dec-50 23:00:00 PST',
+                    'X-Robots-Tag: googlebot: unavailable_after: Saturday, 01-Jul-00 07:00:00 PST'
+                ]
+            ],*/
+            [
+                'http://example.com/',
+                'googlebot',
+                false,
+                [
+                    'X-Robots-Tag: unavailable_after: 31 Dec 2050 23:00:00 PST',
+                    'X-Robots-Tag: googlebot: unavailable_after: 01 Jul 2000 07:00:00 PST'
+                ]
+            ]
+        ];
+    }
+}
diff --git a/test/cases/UserAgentTest.php b/test/cases/UserAgentTest.php
index 457c57b..f035034 100644
--- a/test/cases/UserAgentTest.php
+++ b/test/cases/UserAgentTest.php
@@ -4,7 +4,7 @@
 
 use vipnytt\robot\UserAgentParser;
 
-class UserAgentTests extends \PHPUnit_Framework_TestCase
+class UserAgentTest extends \PHPUnit_Framework_TestCase
 {
     /**
      * Character case
diff --git a/test/cases/exportTest.php b/test/cases/exportTest.php
index d33fc15..db95e6d 100644
--- a/test/cases/exportTest.php
+++ b/test/cases/exportTest.php
@@ -12,21 +12,22 @@ class exportTest extends \PHPUnit_Framework_TestCase
      * @dataProvider generateDataForTest
      * @param string $url
      * @param string $bot
-     * @param string $headers
+     * @param bool $strict
+     * @param array|null $headers
      */
-    public function testExport($url, $bot, $headers)
+    public function testExport($url, $bot, $strict, $headers)
     {
-        $parser = new XRobotsTagParser($url, $bot, $headers);
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
         $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
 
-        $this->assertContains('noindex', $parser->export()['googlebot']);
-        $this->assertContains('noarchive', $parser->export()['googlebot']);
+        $this->assertContains(['noindex' => true], $parser->export()['googlebot']);
+        $this->assertContains(['noarchive' => true], $parser->export()['googlebot']);
 
-        $this->assertContains('noindex', $parser->export()['bingbot']);
-        $this->assertContains('noodp', $parser->export()['bingbot']);
+        $this->assertContains(['noindex' => true], $parser->export()['bingbot']);
+        $this->assertContains(['noodp' => true], $parser->export()['bingbot']);
 
-        $this->assertContains('noindex', $parser->export()['']);
-        $this->assertContains('noodp', $parser->export()['']);
+        $this->assertContains(['noindex' => true], $parser->export()['']);
+        $this->assertContains(['noodp' => true], $parser->export()['']);
     }
 
     /**
@@ -39,6 +40,7 @@ public function generateDataForTest()
             [
                 'http://example.com/',
                 'googlebot',
+                false,
                 [
                     'X-Robots-Tag: googlebot: noindex, noarchive',
                     'X-Robots-Tag: bingbot: noindex, noodp',
diff --git a/test/cases/getRulesTest.php b/test/cases/getRulesTest.php
index f693b45..ab4fe3a 100644
--- a/test/cases/getRulesTest.php
+++ b/test/cases/getRulesTest.php
@@ -12,16 +12,17 @@ class getRulesTest extends \PHPUnit_Framework_TestCase
      * @dataProvider generateDataForTest
      * @param string $url
      * @param string $bot
-     * @param string $headers
+     * @param bool $strict
+     * @param array|null $headers
      */
-    public function testGetRules($url, $bot, $headers)
+    public function testGetRules($url, $bot, $strict, $headers)
     {
-        $parser = new XRobotsTagParser($url, $bot, $headers);
+        $parser = new XRobotsTagParser($url, $bot, $strict, $headers);
         $this->assertInstanceOf('vipnytt\XRobotsTagParser', $parser);
 
-        $this->assertContains('noindex', $parser->getRules());
-        $this->assertContains('noarchive', $parser->getRules());
-        $this->assertContains('noodp', $parser->getRules());
+        $this->assertContains(['noindex' => true], $parser->getRules());
+        $this->assertContains(['noarchive' => true], $parser->getRules());
+        $this->assertContains(['noodp' => true], $parser->getRules());
     }
 
     /**
@@ -34,6 +35,7 @@ public function generateDataForTest()
             [
                 'http://example.com/',
                 'googlebot',
+                false,
                 [
                     'X-Robots-Tag: googlebot: noindex, noarchive',
                     'X-Robots-Tag: bingbot: noindex, noodp',