diff --git a/src/parser/calendar/data/PhutilCalendarRelativeDateTime.php b/src/parser/calendar/data/PhutilCalendarRelativeDateTime.php
index c0b8bff..15c5dc2 100644
--- a/src/parser/calendar/data/PhutilCalendarRelativeDateTime.php
+++ b/src/parser/calendar/data/PhutilCalendarRelativeDateTime.php
@@ -1,71 +1,74 @@
 <?php
 
 final class PhutilCalendarRelativeDateTime
   extends PhutilCalendarProxyDateTime {
 
   private $duration;
 
   public function setOrigin(PhutilCalendarDateTime $origin) {
     return $this->setProxy($origin);
   }
 
   public function getOrigin() {
     return $this->getProxy();
   }
 
   public function setDuration(PhutilCalendarDuration $duration) {
     $this->duration = $duration;
     return $this;
   }
 
   public function getDuration() {
     return $this->duration;
   }
 
   public function newPHPDateTime() {
     $datetime = parent::newPHPDateTime();
     $duration = $this->getDuration();
 
     if ($duration->getIsNegative()) {
       $sign = '-';
     } else {
       $sign = '+';
     }
 
     $map = array(
       'weeks' => $duration->getWeeks(),
       'days' => $duration->getDays(),
       'hours' => $duration->getHours(),
       'minutes' => $duration->getMinutes(),
       'seconds' => $duration->getSeconds(),
     );
 
     foreach ($map as $unit => $value) {
       if (!$value) {
         continue;
       }
       $datetime->modify("{$sign}{$value} {$unit}");
     }
 
     return $datetime;
   }
 
   public function newAbsoluteDateTime() {
     $clone = clone $this;
-    $clone->setViewerTimezone(null);
+
+    if ($clone->getTimezone()) {
+      $clone->setViewerTimezone(null);
+    }
 
     $datetime = $clone->newPHPDateTime();
 
     return id(new PhutilCalendarAbsoluteDateTime())
       ->setYear((int)$datetime->format('Y'))
       ->setMonth((int)$datetime->format('m'))
       ->setDay((int)$datetime->format('d'))
       ->setHour((int)$datetime->format('H'))
       ->setMinute((int)$datetime->format('i'))
       ->setSecond((int)$datetime->format('s'))
       ->setIsAllDay($clone->getIsAllDay())
       ->setTimezone($clone->getTimezone())
       ->setViewerTimezone($this->getViewerTimezone());
   }
 
 }
diff --git a/src/parser/calendar/data/__tests__/PhutilCalendarDateTimeTestCase.php b/src/parser/calendar/data/__tests__/PhutilCalendarDateTimeTestCase.php
index 1337a2a..d80aef9 100644
--- a/src/parser/calendar/data/__tests__/PhutilCalendarDateTimeTestCase.php
+++ b/src/parser/calendar/data/__tests__/PhutilCalendarDateTimeTestCase.php
@@ -1,29 +1,49 @@
 <?php
 
 final class PhutilCalendarDateTimeTestCase extends PhutilTestCase {
 
   public function testDateTimeDuration() {
     $start = PhutilCalendarAbsoluteDateTime::newFromISO8601('20161128T090000Z')
       ->setTimezone('America/Los_Angeles')
       ->setViewerTimezone('America/Chicago')
       ->setIsAllDay(true);
 
     $this->assertEqual(
       '20161128',
       $start->getISO8601());
 
     $end = $start
       ->newAbsoluteDateTime()
       ->setHour(0)
       ->setMinute(0)
       ->setSecond(0)
       ->newRelativeDateTime('P1D')
       ->newAbsoluteDateTime();
 
     $this->assertEqual(
       '20161129',
       $end->getISO8601());
+
+    // This is a date which explicitly has no specified timezone.
+    $start = PhutilCalendarAbsoluteDateTime::newFromISO8601('20161128', null)
+      ->setViewerTimezone('UTC');
+
+    $this->assertEqual(
+      '20161128',
+      $start->getISO8601());
+
+    $end = $start
+      ->newAbsoluteDateTime()
+      ->setHour(0)
+      ->setMinute(0)
+      ->setSecond(0)
+      ->newRelativeDateTime('P1D')
+      ->newAbsoluteDateTime();
+
+    $this->assertEqual(
+      '20161129',
+      $end->getISO8601());
   }
 
 
 }
diff --git a/src/parser/calendar/ics/__tests__/PhutilICSParserTestCase.php b/src/parser/calendar/ics/__tests__/PhutilICSParserTestCase.php
index 8c6a705..e99acaf 100644
--- a/src/parser/calendar/ics/__tests__/PhutilICSParserTestCase.php
+++ b/src/parser/calendar/ics/__tests__/PhutilICSParserTestCase.php
@@ -1,315 +1,341 @@
 <?php
 
 final class PhutilICSParserTestCase extends PhutilTestCase {
 
   public function testICSParser() {
     $event = $this->parseICSSingleEvent('simple.ics');
 
     $this->assertEqual(
       array(
         array(
           'name' => 'CREATED',
           'parameters' => array(),
           'value' => array(
             'type' => 'DATE-TIME',
             'value' => array(
               '20160908T172702Z',
             ),
             'raw' => '20160908T172702Z',
           ),
         ),
         array(
           'name' => 'UID',
           'parameters' => array(),
           'value' => array(
             'type' => 'TEXT',
             'value' => array(
               '1CEB57AF-0C9C-402D-B3BD-D75BD4843F68',
             ),
             'raw' => '1CEB57AF-0C9C-402D-B3BD-D75BD4843F68',
           ),
         ),
         array(
           'name' => 'DTSTART',
           'parameters' => array(
             array(
               'name' => 'TZID',
               'values' => array(
                 array(
                   'value' => 'America/Los_Angeles',
                   'quoted' => false,
                 ),
               ),
             ),
           ),
           'value' => array(
             'type' => 'DATE-TIME',
             'value' => array(
               '20160915T090000',
             ),
             'raw' => '20160915T090000',
           ),
         ),
         array(
           'name' => 'DTEND',
           'parameters' => array(
             array(
               'name' => 'TZID',
               'values' => array(
                 array(
                   'value' => 'America/Los_Angeles',
                   'quoted' => false,
                 ),
               ),
             ),
           ),
           'value' => array(
             'type' => 'DATE-TIME',
             'value' => array(
               '20160915T100000',
             ),
             'raw' => '20160915T100000',
           ),
         ),
         array(
           'name' => 'SUMMARY',
           'parameters' => array(),
           'value' => array(
             'type' => 'TEXT',
             'value' => array(
               'Simple Event',
             ),
             'raw' => 'Simple Event',
           ),
         ),
         array(
           'name' => 'DESCRIPTION',
           'parameters' => array(),
           'value' => array(
             'type' => 'TEXT',
             'value' => array(
               'This is a simple event.',
             ),
             'raw' => 'This is a simple event.',
           ),
         ),
       ),
       $event->getAttribute('ics.properties'));
 
     $this->assertEqual(
       'Simple Event',
       $event->getName());
 
     $this->assertEqual(
       'This is a simple event.',
       $event->getDescription());
 
     $this->assertEqual(
       1473955200,
       $event->getStartDateTime()->getEpoch());
 
     $this->assertEqual(
       1473955200 + phutil_units('1 hour in seconds'),
       $event->getEndDateTime()->getEpoch());
   }
 
   public function testICSOddTimezone() {
     $event = $this->parseICSSingleEvent('zimbra-timezone.ics');
 
     $start = $event->getStartDateTime();
 
     $this->assertEqual(
       '20170303T140000Z',
       $start->getISO8601());
   }
 
   public function testICSFloatingTime() {
     // This tests "floating" event times, which have no absolute time and are
     // supposed to be interpreted using the viewer's timezone. It also uses
     // a duration, and the duration needs to float along with the viewer
     // timezone.
 
     $event = $this->parseICSSingleEvent('floating.ics');
 
     $start = $event->getStartDateTime();
 
     $caught = null;
     try {
       $start->getEpoch();
     } catch (Exception $ex) {
       $caught = $ex;
     }
 
     $this->assertTrue(
       ($caught instanceof Exception),
       pht('Expected exception for floating time with no viewer timezone.'));
 
     $newyears_utc = strtotime('2015-01-01 00:00:00 UTC');
     $this->assertEqual(1420070400, $newyears_utc);
 
     $start->setViewerTimezone('UTC');
     $this->assertEqual(
       $newyears_utc,
       $start->getEpoch());
 
     $start->setViewerTimezone('America/Los_Angeles');
     $this->assertEqual(
       $newyears_utc + phutil_units('8 hours in seconds'),
       $start->getEpoch());
 
     $start->setViewerTimezone('America/New_York');
     $this->assertEqual(
       $newyears_utc + phutil_units('5 hours in seconds'),
       $start->getEpoch());
 
     $end = $event->getEndDateTime();
     $end->setViewerTimezone('UTC');
     $this->assertEqual(
       $newyears_utc + phutil_units('24 hours in seconds'),
       $end->getEpoch());
 
     $end->setViewerTimezone('America/Los_Angeles');
     $this->assertEqual(
       $newyears_utc + phutil_units('32 hours in seconds'),
       $end->getEpoch());
 
     $end->setViewerTimezone('America/New_York');
     $this->assertEqual(
       $newyears_utc + phutil_units('29 hours in seconds'),
       $end->getEpoch());
   }
 
   public function testICSVALARM() {
     $event = $this->parseICSSingleEvent('valarm.ics');
 
     // For now, we parse but ignore VALARM sections. This test just makes
     // sure they survive parsing.
 
     $start_epoch = strtotime('2016-10-19 22:00:00 UTC');
     $this->assertEqual(1476914400, $start_epoch);
 
     $this->assertEqual(
       $start_epoch,
       $event->getStartDateTime()->getEpoch());
   }
 
   public function testICSDuration() {
     $event = $this->parseICSSingleEvent('duration.ics');
 
     // Raw value is "20160719T095722Z".
     $start_epoch = strtotime('2016-07-19 09:57:22 UTC');
     $this->assertEqual(1468922242, $start_epoch);
 
     // Raw value is "P1DT17H4M23S".
     $duration =
       phutil_units('1 day in seconds') +
       phutil_units('17 hours in seconds') +
       phutil_units('4 minutes in seconds') +
       phutil_units('23 seconds in seconds');
 
     $this->assertEqual(
       $start_epoch,
       $event->getStartDateTime()->getEpoch());
 
     $this->assertEqual(
       $start_epoch + $duration,
       $event->getEndDateTime()->getEpoch());
   }
 
+  public function testICSWeeklyEvent() {
+    $event = $this->parseICSSingleEvent('weekly.ics');
+
+    $start = $event->getStartDateTime();
+    $start->setViewerTimezone('UTC');
+
+    $rrule = $event->getRecurrenceRule()
+      ->setStartDateTime($start);
+
+    $rset = id(new PhutilCalendarRecurrenceSet())
+      ->addSource($rrule);
+
+    $result = $rset->getEventsBetween(null, null, 3);
+
+    $expect = array(
+      PhutilCalendarAbsoluteDateTime::newFromISO8601('20150811'),
+      PhutilCalendarAbsoluteDateTime::newFromISO8601('20150818'),
+      PhutilCalendarAbsoluteDateTime::newFromISO8601('20150825'),
+    );
+
+    $this->assertEqual(
+      mpull($expect, 'getISO8601'),
+      mpull($result, 'getISO8601'),
+      pht('Weekly recurring event.'));
+  }
+
   public function testICSParserErrors() {
     $map = array(
       'err-missing-end.ics' => PhutilICSParser::PARSE_MISSING_END,
       'err-bad-base64.ics' => PhutilICSParser::PARSE_BAD_BASE64,
       'err-bad-boolean.ics' => PhutilICSParser::PARSE_BAD_BOOLEAN,
       'err-extra-end.ics' => PhutilICSParser::PARSE_EXTRA_END,
       'err-initial-unfold.ics' => PhutilICSParser::PARSE_INITIAL_UNFOLD,
       'err-malformed-double-quote.ics' =>
         PhutilICSParser::PARSE_MALFORMED_DOUBLE_QUOTE,
       'err-malformed-parameter.ics' =>
         PhutilICSParser::PARSE_MALFORMED_PARAMETER_NAME,
       'err-malformed-property.ics' =>
         PhutilICSParser::PARSE_MALFORMED_PROPERTY,
       'err-missing-value.ics' => PhutilICSParser::PARSE_MISSING_VALUE,
       'err-mixmatched-sections.ics' =>
         PhutilICSParser::PARSE_MISMATCHED_SECTIONS,
       'err-root-property.ics' => PhutilICSParser::PARSE_ROOT_PROPERTY,
       'err-unescaped-backslash.ics' =>
         PhutilICSParser::PARSE_UNESCAPED_BACKSLASH,
       'err-unexpected-text.ics' => PhutilICSParser::PARSE_UNEXPECTED_TEXT,
       'err-multiple-parameters.ics' =>
         PhutilICSParser::PARSE_MULTIPLE_PARAMETERS,
       'err-empty-datetime.ics' =>
         PhutilICSParser::PARSE_EMPTY_DATETIME,
       'err-many-datetime.ics' =>
         PhutilICSParser::PARSE_MANY_DATETIME,
       'err-bad-datetime.ics' =>
         PhutilICSParser::PARSE_BAD_DATETIME,
       'err-empty-duration.ics' =>
         PhutilICSParser::PARSE_EMPTY_DURATION,
       'err-many-duration.ics' =>
         PhutilICSParser::PARSE_MANY_DURATION,
       'err-bad-duration.ics' =>
         PhutilICSParser::PARSE_BAD_DURATION,
 
       'simple.ics' => null,
       'good-boolean.ics' => null,
       'multiple-vcalendars.ics' => null,
     );
 
     foreach ($map as $test_file => $expect) {
       $caught = null;
       try {
         $this->parseICSDocument($test_file);
       } catch (PhutilICSParserException $ex) {
         $caught = $ex;
       }
 
       if ($expect === null) {
         $this->assertTrue(
           ($caught === null),
           pht(
             'Expected no exception parsing "%s", got: %s',
             $test_file,
             (string)$ex));
       } else {
         if ($caught) {
           $code = $ex->getParserFailureCode();
           $explain = pht(
             'Expected one exception parsing "%s", got a different '.
             'one: %s',
             $test_file,
             (string)$ex);
         } else {
           $code = null;
           $explain = pht(
             'Expected exception parsing "%s", got none.',
             $test_file);
         }
 
         $this->assertEqual($expect, $code, $explain);
       }
     }
   }
 
   private function parseICSSingleEvent($name) {
     $root = $this->parseICSDocument($name);
 
     $documents = $root->getDocuments();
     $this->assertEqual(1, count($documents));
     $document = head($documents);
 
     $events = $document->getEvents();
     $this->assertEqual(1, count($events));
 
     return head($events);
   }
 
   private function parseICSDocument($name) {
     $path = dirname(__FILE__).'/data/'.$name;
     $data = Filesystem::readFile($path);
     return id(new PhutilICSParser())
       ->parseICSData($data);
   }
 
 
 }
diff --git a/src/parser/calendar/ics/__tests__/data/weekly.ics b/src/parser/calendar/ics/__tests__/data/weekly.ics
new file mode 100644
index 0000000..8e067bf
--- /dev/null
+++ b/src/parser/calendar/ics/__tests__/data/weekly.ics
@@ -0,0 +1,14 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+BEGIN:VEVENT
+TRANSP:OPAQUE
+DTEND;VALUE=DATE:20150812
+LAST-MODIFIED:20160822T130015Z
+UID:4AE69E91-4A51-4B77-8849-85981E037A83
+DTSTAMP:20161129T152151Z
+SUMMARY:Weekly Event
+DTSTART;VALUE=DATE:20150811
+CREATED:20141109T163445Z
+RRULE:FREQ=WEEKLY
+END:VEVENT
+END:VCALENDAR