diff --git a/resources/sql/autopatches/20161005.cal.01.rrules.php b/resources/sql/autopatches/20161005.cal.01.rrules.php
new file mode 100644
index 0000000000..e2e61ba30a
--- /dev/null
+++ b/resources/sql/autopatches/20161005.cal.01.rrules.php
@@ -0,0 +1,44 @@
+<?php
+
+$table = new PhabricatorCalendarEvent();
+$conn = $table->establishConnection('w');
+$table_name = 'calendar_event';
+
+foreach (new LiskRawMigrationIterator($conn, $table_name) as $row) {
+  $parameters = phutil_json_decode($row['parameters']);
+  if (isset($parameters['recurrenceRule'])) {
+    // This event has already been migrated.
+    continue;
+  }
+
+  if (!$row['isRecurring']) {
+    continue;
+  }
+
+  $old_rule = $row['recurrenceFrequency'];
+  if (!$old_rule) {
+    continue;
+  }
+
+  try {
+    $frequency = phutil_json_decode($old_rule);
+    if ($frequency) {
+      $frequency_rule = $frequency['rule'];
+      $frequency_rule = phutil_utf8_strtoupper($frequency_rule);
+
+      $rrule = id(new PhutilCalendarRecurrenceRule())
+        ->setFrequency($frequency_rule);
+    }
+  } catch (Exception $ex) {
+    continue;
+  }
+
+  $parameters['recurrenceRule'] = $rrule->toDictionary();
+
+  queryfx(
+    $conn,
+    'UPDATE %T SET parameters = %s WHERE id = %d',
+    $table_name,
+    phutil_json_encode($parameters),
+    $row['id']);
+}
diff --git a/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php b/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
index 8f7ee8929e..2a1e08ae89 100644
--- a/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
+++ b/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
@@ -1,530 +1,537 @@
 <?php
 
 final class PhabricatorCalendarEventViewController
   extends PhabricatorCalendarController {
 
   public function shouldAllowPublic() {
     return true;
   }
 
   public function handleRequest(AphrontRequest $request) {
     $viewer = $request->getViewer();
 
     $event = $this->loadEvent();
     if (!$event) {
       return new Aphront404Response();
     }
 
     // If we looked up or generated a stub event, redirect to that event's
     // canonical URI.
     $id = $request->getURIData('id');
     if ($event->getID() != $id) {
       $uri = $event->getURI();
       return id(new AphrontRedirectResponse())->setURI($uri);
     }
 
     $monogram = $event->getMonogram();
     $page_title = $monogram.' '.$event->getName();
     $crumbs = $this->buildApplicationCrumbs();
 
     $start = $event->newStartDateTime()
       ->newPHPDateTime();
 
     $crumbs->addTextCrumb(
       $start->format('F Y'),
       '/calendar/query/month/'.$start->format('Y/m/'));
 
     $crumbs->addTextCrumb(
       $start->format('D jS'),
       '/calendar/query/month/'.$start->format('Y/m/d/'));
 
     $crumbs->addTextCrumb($monogram);
     $crumbs->setBorder(true);
 
     $timeline = $this->buildTransactionTimeline(
       $event,
       new PhabricatorCalendarEventTransactionQuery());
 
     $header = $this->buildHeaderView($event);
     $subheader = $this->buildSubheaderView($event);
     $curtain = $this->buildCurtain($event);
     $details = $this->buildPropertySection($event);
     $recurring = $this->buildRecurringSection($event);
     $description = $this->buildDescriptionView($event);
 
     $comment_view = id(new PhabricatorCalendarEventEditEngine())
       ->setViewer($viewer)
       ->buildEditEngineCommentView($event);
 
     $timeline->setQuoteRef($monogram);
     $comment_view->setTransactionTimeline($timeline);
 
     $details_header = id(new PHUIHeaderView())
       ->setHeader(pht('Details'));
     $recurring_header = $this->buildRecurringHeader($event);
 
     $view = id(new PHUITwoColumnView())
       ->setHeader($header)
       ->setSubheader($subheader)
       ->setMainColumn(
         array(
           $timeline,
           $comment_view,
         ))
       ->setCurtain($curtain)
       ->addPropertySection($details_header, $details)
       ->addPropertySection($recurring_header, $recurring)
       ->addPropertySection(pht('Description'), $description);
 
     return $this->newPage()
       ->setTitle($page_title)
       ->setCrumbs($crumbs)
       ->setPageObjectPHIDs(array($event->getPHID()))
       ->appendChild($view);
   }
 
   private function buildHeaderView(
     PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
     $id = $event->getID();
 
     if ($event->isCancelledEvent()) {
       $icon = 'fa-ban';
       $color = 'red';
       $status = pht('Cancelled');
     } else {
       $icon = 'fa-check';
       $color = 'bluegrey';
       $status = pht('Active');
     }
 
     $header = id(new PHUIHeaderView())
       ->setUser($viewer)
       ->setHeader($event->getName())
       ->setStatus($icon, $color, $status)
       ->setPolicyObject($event)
       ->setHeaderIcon($event->getIcon());
 
     foreach ($this->buildRSVPActions($event) as $action) {
       $header->addActionLink($action);
     }
 
     return $header;
   }
 
   private function buildCurtain(PhabricatorCalendarEvent $event) {
     $viewer = $this->getRequest()->getUser();
     $id = $event->getID();
     $is_attending = $event->getIsUserAttending($viewer->getPHID());
 
     $can_edit = PhabricatorPolicyFilter::hasCapability(
       $viewer,
       $event,
       PhabricatorPolicyCapability::CAN_EDIT);
 
     $edit_uri = "event/edit/{$id}/";
     if ($event->isChildEvent()) {
       $edit_label = pht('Edit This Instance');
     } else {
       $edit_label = pht('Edit Event');
     }
 
     $curtain = $this->newCurtainView($event);
 
     if ($edit_label && $edit_uri) {
       $curtain->addAction(
         id(new PhabricatorActionView())
           ->setName($edit_label)
           ->setIcon('fa-pencil')
           ->setHref($this->getApplicationURI($edit_uri))
           ->setDisabled(!$can_edit)
           ->setWorkflow(!$can_edit));
     }
 
     if ($is_attending) {
       $curtain->addAction(
         id(new PhabricatorActionView())
           ->setName(pht('Decline Event'))
           ->setIcon('fa-user-times')
           ->setHref($this->getApplicationURI("event/join/{$id}/"))
           ->setWorkflow(true));
     } else {
       $curtain->addAction(
         id(new PhabricatorActionView())
           ->setName(pht('Join Event'))
           ->setIcon('fa-user-plus')
           ->setHref($this->getApplicationURI("event/join/{$id}/"))
           ->setWorkflow(true));
     }
 
     $cancel_uri = $this->getApplicationURI("event/cancel/{$id}/");
     $cancel_disabled = !$can_edit;
 
     if ($event->isChildEvent()) {
       $cancel_label = pht('Cancel This Instance');
       $reinstate_label = pht('Reinstate This Instance');
 
       if ($event->getParentEvent()->getIsCancelled()) {
         $cancel_disabled = true;
       }
     } else if ($event->isParentEvent()) {
       $cancel_label = pht('Cancel All');
       $reinstate_label = pht('Reinstate All');
     } else {
       $cancel_label = pht('Cancel Event');
       $reinstate_label = pht('Reinstate Event');
     }
 
     if ($event->isCancelledEvent()) {
       $curtain->addAction(
         id(new PhabricatorActionView())
           ->setName($reinstate_label)
           ->setIcon('fa-plus')
           ->setHref($cancel_uri)
           ->setDisabled($cancel_disabled)
           ->setWorkflow(true));
     } else {
       $curtain->addAction(
         id(new PhabricatorActionView())
           ->setName($cancel_label)
           ->setIcon('fa-times')
           ->setHref($cancel_uri)
           ->setDisabled($cancel_disabled)
           ->setWorkflow(true));
     }
 
     $ics_name = $event->getICSFilename();
     $export_uri = $this->getApplicationURI("event/export/{$id}/{$ics_name}");
 
     $curtain->addAction(
       id(new PhabricatorActionView())
         ->setName(pht('Export as .ics'))
         ->setIcon('fa-download')
         ->setHref($export_uri));
 
     return $curtain;
   }
 
   private function buildPropertySection(
     PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
 
     $properties = id(new PHUIPropertyListView())
       ->setUser($viewer);
 
     $invitees = $event->getInvitees();
     foreach ($invitees as $key => $invitee) {
       if ($invitee->isUninvited()) {
         unset($invitees[$key]);
       }
     }
 
     if ($invitees) {
       $invitee_list = new PHUIStatusListView();
 
       $icon_invited = PHUIStatusItemView::ICON_OPEN;
       $icon_attending = PHUIStatusItemView::ICON_ACCEPT;
       $icon_declined = PHUIStatusItemView::ICON_REJECT;
 
       $status_invited = PhabricatorCalendarEventInvitee::STATUS_INVITED;
       $status_attending = PhabricatorCalendarEventInvitee::STATUS_ATTENDING;
       $status_declined = PhabricatorCalendarEventInvitee::STATUS_DECLINED;
 
       $icon_map = array(
         $status_invited => $icon_invited,
         $status_attending => $icon_attending,
         $status_declined => $icon_declined,
       );
 
       $icon_color_map = array(
         $status_invited => null,
         $status_attending => 'green',
         $status_declined => 'red',
       );
 
       foreach ($invitees as $invitee) {
         $item = new PHUIStatusItemView();
         $invitee_phid = $invitee->getInviteePHID();
         $status = $invitee->getStatus();
         $target = $viewer->renderHandle($invitee_phid);
         $icon = $icon_map[$status];
         $icon_color = $icon_color_map[$status];
 
         $item->setIcon($icon, $icon_color)
           ->setTarget($target);
         $invitee_list->addItem($item);
       }
     } else {
       $invitee_list = phutil_tag(
         'em',
         array(),
         pht('None'));
     }
 
     $properties->addProperty(
       pht('Invitees'),
       $invitee_list);
 
     $properties->invokeWillRenderEvent();
 
     return $properties;
   }
 
   private function buildRecurringHeader(PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
 
     if (!$event->getIsRecurring()) {
       return null;
     }
 
     $header = id(new PHUIHeaderView())
       ->setHeader(pht('Recurring Event'));
 
     $sequence = $event->getSequenceIndex();
     if ($event->isParentEvent()) {
       $parent = $event;
     } else {
       $parent = $event->getParentEvent();
     }
 
     if ($parent->isValidSequenceIndex($viewer, $sequence + 1)) {
       $next_uri = $parent->getURI().'/'.($sequence + 1);
       $has_next = true;
     } else {
       $next_uri = null;
       $has_next = false;
     }
 
     if ($sequence) {
       if ($sequence > 1) {
         $previous_uri = $parent->getURI().'/'.($sequence - 1);
       } else {
         $previous_uri = $parent->getURI();
       }
       $has_previous = true;
     } else {
       $has_previous = false;
       $previous_uri = null;
     }
 
     $prev_button = id(new PHUIButtonView())
       ->setTag('a')
       ->setIcon('fa-chevron-left')
       ->setHref($previous_uri)
       ->setDisabled(!$has_previous)
       ->setText(pht('Previous'));
 
     $next_button = id(new PHUIButtonView())
       ->setTag('a')
       ->setIcon('fa-chevron-right')
       ->setHref($next_uri)
       ->setDisabled(!$has_next)
       ->setText(pht('Next'));
 
     $header
       ->addActionLink($next_button)
       ->addActionLink($prev_button);
 
     return $header;
   }
 
   private function buildRecurringSection(PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
 
     if (!$event->getIsRecurring()) {
       return null;
     }
 
     $properties = id(new PHUIPropertyListView())
       ->setUser($viewer);
 
     $is_parent = $event->isParentEvent();
     if ($is_parent) {
       $parent_link = null;
     } else {
       $parent = $event->getParentEvent();
       $parent_link = $viewer
         ->renderHandle($parent->getPHID())
         ->render();
     }
 
-    $rule = $event->getFrequencyRule();
-    switch ($rule) {
-      case PhabricatorCalendarEvent::FREQUENCY_DAILY:
+    $rrule = $event->newRecurrenceRule();
+
+    if ($rrule) {
+      $frequency = $rrule->getFrequency();
+    } else {
+      $frequency = null;
+    }
+
+    switch ($frequency) {
+      case PhutilCalendarRecurrenceRule::FREQUENCY_DAILY:
         if ($is_parent) {
           $message = pht('This event repeats every day.');
         } else {
           $message = pht(
             'This event is an instance of %s, and repeats every day.',
             $parent_link);
         }
         break;
-      case PhabricatorCalendarEvent::FREQUENCY_WEEKLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_WEEKLY:
         if ($is_parent) {
           $message = pht('This event repeats every week.');
         } else {
           $message = pht(
             'This event is an instance of %s, and repeats every week.',
             $parent_link);
         }
         break;
-      case PhabricatorCalendarEvent::FREQUENCY_MONTHLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_MONTHLY:
         if ($is_parent) {
           $message = pht('This event repeats every month.');
         } else {
           $message = pht(
             'This event is an instance of %s, and repeats every month.',
             $parent_link);
         }
         break;
-      case PhabricatorCalendarEvent::FREQUENCY_YEARLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_YEARLY:
         if ($is_parent) {
           $message = pht('This event repeats every year.');
         } else {
           $message = pht(
             'This event is an instance of %s, and repeats every year.',
             $parent_link);
         }
         break;
     }
 
     $properties->addProperty(pht('Event Series'), $message);
 
     return $properties;
   }
 
   private function buildDescriptionView(
     PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
 
     $properties = id(new PHUIPropertyListView())
       ->setUser($viewer);
 
     if (strlen($event->getDescription())) {
       $description = new PHUIRemarkupView($viewer, $event->getDescription());
       $properties->addTextContent($description);
       return $properties;
     }
 
     return null;
   }
 
   private function loadEvent() {
     $request = $this->getRequest();
     $viewer = $this->getViewer();
 
     $id = $request->getURIData('id');
     $sequence = $request->getURIData('sequence');
 
     // We're going to figure out which event you're trying to look at. Most of
     // the time this is simple, but you may be looking at an instance of a
     // recurring event which we haven't generated an object for.
 
     // If you are, we're going to generate a "stub" event so we have a real
     // ID and PHID to work with, since the rest of the infrastructure relies
     // on these identifiers existing.
 
     // Load the event identified by ID first.
     $event = id(new PhabricatorCalendarEventQuery())
       ->setViewer($viewer)
       ->withIDs(array($id))
       ->executeOne();
     if (!$event) {
       return null;
     }
 
     // If we aren't looking at an instance of this event, this is a completely
     // normal request and we can just return this event.
     if (!$sequence) {
       return $event;
     }
 
     // When you view "E123/999", E123 is normally the parent event. However,
     // you might visit a different instance first instead and then fiddle
     // with the URI. If the event we're looking at is a child, we are going
     // to act on the parent instead.
     if ($event->isChildEvent()) {
       $event = $event->getParentEvent();
     }
 
     // Try to load the instance. If it already exists, we're all done and
     // can just return it.
     $instance = id(new PhabricatorCalendarEventQuery())
       ->setViewer($viewer)
       ->withInstanceSequencePairs(
         array(
           array($event->getPHID(), $sequence),
         ))
       ->executeOne();
     if ($instance) {
       return $instance;
     }
 
     if (!$viewer->isLoggedIn()) {
       throw new Exception(
         pht(
           'This event instance has not been created yet. Log in to create '.
           'it.'));
     }
 
     if (!$event->isValidSequenceIndex($viewer, $sequence)) {
       return null;
     }
 
     return $event->newStub($viewer, $sequence);
   }
 
   private function buildSubheaderView(PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
 
     $host_phid = $event->getHostPHID();
 
     $handles = $viewer->loadHandles(array($host_phid));
     $handle = $handles[$host_phid];
 
     $host = $viewer->renderHandle($host_phid);
     $host = phutil_tag('strong', array(), $host);
 
     $image_uri = $handles[$host_phid]->getImageURI();
     $image_href = $handles[$host_phid]->getURI();
 
     $date = $event->renderEventDate($viewer, true);
 
     $content = pht('Hosted by %s on %s.', $host, $date);
 
     return id(new PHUIHeadThingView())
       ->setImage($image_uri)
       ->setImageHref($image_href)
       ->setContent($content);
   }
 
 
   private function buildRSVPActions(PhabricatorCalendarEvent $event) {
     $viewer = $this->getViewer();
     $id = $event->getID();
 
     $invite_status = $event->getUserInviteStatus($viewer->getPHID());
     $status_invited = PhabricatorCalendarEventInvitee::STATUS_INVITED;
     $is_invite_pending = ($invite_status == $status_invited);
     if (!$is_invite_pending) {
       return array();
     }
 
     $decline_button = id(new PHUIButtonView())
       ->setTag('a')
       ->setIcon('fa-times grey')
       ->setHref($this->getApplicationURI("/event/decline/{$id}/"))
       ->setWorkflow(true)
       ->setText(pht('Decline'));
 
     $accept_button = id(new PHUIButtonView())
       ->setTag('a')
       ->setIcon('fa-check green')
       ->setHref($this->getApplicationURI("/event/accept/{$id}/"))
       ->setWorkflow(true)
       ->setText(pht('Accept'));
 
     return array($decline_button, $accept_button);
   }
 
 }
diff --git a/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php b/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
index 63d33beab4..17ea7552e9 100644
--- a/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
+++ b/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
@@ -1,256 +1,264 @@
 <?php
 
 final class PhabricatorCalendarEventEditEngine
   extends PhabricatorEditEngine {
 
   const ENGINECONST = 'calendar.event';
 
   public function getEngineName() {
     return pht('Calendar Events');
   }
 
   public function getSummaryHeader() {
     return pht('Configure Calendar Event Forms');
   }
 
   public function getSummaryText() {
     return pht('Configure how users create and edit events.');
   }
 
   public function getEngineApplicationClass() {
     return 'PhabricatorCalendarApplication';
   }
 
   protected function newEditableObject() {
     return PhabricatorCalendarEvent::initializeNewCalendarEvent(
       $this->getViewer());
   }
 
   protected function newObjectQuery() {
     return new PhabricatorCalendarEventQuery();
   }
 
   protected function getObjectCreateTitleText($object) {
     return pht('Create New Event');
   }
 
   protected function getObjectEditTitleText($object) {
     return pht('Edit Event: %s', $object->getName());
   }
 
   protected function getObjectEditShortText($object) {
     return $object->getMonogram();
   }
 
   protected function getObjectCreateShortText() {
     return pht('Create Event');
   }
 
   protected function getObjectName() {
     return pht('Event');
   }
 
   protected function getObjectViewURI($object) {
     return $object->getURI();
   }
 
   protected function getEditorURI() {
     return $this->getApplication()->getApplicationURI('event/edit/');
   }
 
   protected function buildCustomEditFields($object) {
     $viewer = $this->getViewer();
 
     if ($this->getIsCreate()) {
       $invitee_phids = array($viewer->getPHID());
     } else {
       $invitee_phids = $object->getInviteePHIDsForEdit();
     }
 
     $frequency_options = array(
-      PhabricatorCalendarEvent::FREQUENCY_DAILY => pht('Daily'),
-      PhabricatorCalendarEvent::FREQUENCY_WEEKLY => pht('Weekly'),
-      PhabricatorCalendarEvent::FREQUENCY_MONTHLY => pht('Monthly'),
-      PhabricatorCalendarEvent::FREQUENCY_YEARLY => pht('Yearly'),
+      PhutilCalendarRecurrenceRule::FREQUENCY_DAILY => pht('Daily'),
+      PhutilCalendarRecurrenceRule::FREQUENCY_WEEKLY => pht('Weekly'),
+      PhutilCalendarRecurrenceRule::FREQUENCY_MONTHLY => pht('Monthly'),
+      PhutilCalendarRecurrenceRule::FREQUENCY_YEARLY => pht('Yearly'),
     );
 
     $fields = array(
       id(new PhabricatorTextEditField())
         ->setKey('name')
         ->setLabel(pht('Name'))
         ->setDescription(pht('Name of the event.'))
         ->setIsRequired(true)
         ->setTransactionType(
           PhabricatorCalendarEventNameTransaction::TRANSACTIONTYPE)
         ->setConduitDescription(pht('Rename the event.'))
         ->setConduitTypeDescription(pht('New event name.'))
         ->setValue($object->getName()),
       id(new PhabricatorRemarkupEditField())
         ->setKey('description')
         ->setLabel(pht('Description'))
         ->setDescription(pht('Description of the event.'))
         ->setTransactionType(
           PhabricatorCalendarEventDescriptionTransaction::TRANSACTIONTYPE)
         ->setConduitDescription(pht('Update the event description.'))
         ->setConduitTypeDescription(pht('New event description.'))
         ->setValue($object->getDescription()),
       id(new PhabricatorBoolEditField())
         ->setKey('cancelled')
         ->setOptions(pht('Active'), pht('Cancelled'))
         ->setLabel(pht('Cancelled'))
         ->setDescription(pht('Cancel the event.'))
         ->setTransactionType(
           PhabricatorCalendarEventCancelTransaction::TRANSACTIONTYPE)
         ->setIsConduitOnly(true)
         ->setConduitDescription(pht('Cancel or restore the event.'))
         ->setConduitTypeDescription(pht('True to cancel the event.'))
         ->setValue($object->getIsCancelled()),
       id(new PhabricatorUsersEditField())
         ->setKey('hostPHID')
         ->setAliases(array('host'))
         ->setLabel(pht('Host'))
         ->setDescription(pht('Host of the event.'))
         ->setTransactionType(
           PhabricatorCalendarEventHostTransaction::TRANSACTIONTYPE)
         ->setIsConduitOnly($this->getIsCreate())
         ->setConduitDescription(pht('Change the host of the event.'))
         ->setConduitTypeDescription(pht('New event host.'))
         ->setSingleValue($object->getHostPHID()),
       id(new PhabricatorDatasourceEditField())
         ->setKey('inviteePHIDs')
         ->setAliases(array('invite', 'invitee', 'invitees', 'inviteePHID'))
         ->setLabel(pht('Invitees'))
         ->setDatasource(new PhabricatorMetaMTAMailableDatasource())
         ->setTransactionType(
           PhabricatorCalendarEventInviteTransaction::TRANSACTIONTYPE)
         ->setDescription(pht('Users invited to the event.'))
         ->setConduitDescription(pht('Change invited users.'))
         ->setConduitTypeDescription(pht('New event invitees.'))
         ->setValue($invitee_phids)
         ->setCommentActionLabel(pht('Change Invitees')),
     );
 
     if ($this->getIsCreate()) {
       $fields[] = id(new PhabricatorBoolEditField())
         ->setKey('isRecurring')
         ->setLabel(pht('Recurring'))
         ->setOptions(pht('One-Time Event'), pht('Recurring Event'))
         ->setTransactionType(
           PhabricatorCalendarEventRecurringTransaction::TRANSACTIONTYPE)
         ->setDescription(pht('One time or recurring event.'))
         ->setConduitDescription(pht('Make the event recurring.'))
         ->setConduitTypeDescription(pht('Mark the event as a recurring event.'))
         ->setValue($object->getIsRecurring());
 
+
+      $rrule = $object->newRecurrenceRule();
+      if ($rrule) {
+        $frequency = $rrule->getFrequency();
+      } else {
+        $frequency = null;
+      }
+
       $fields[] = id(new PhabricatorSelectEditField())
         ->setKey('frequency')
         ->setLabel(pht('Frequency'))
         ->setOptions($frequency_options)
         ->setTransactionType(
           PhabricatorCalendarEventFrequencyTransaction::TRANSACTIONTYPE)
         ->setDescription(pht('Recurring event frequency.'))
         ->setConduitDescription(pht('Change the event frequency.'))
         ->setConduitTypeDescription(pht('New event frequency.'))
-        ->setValue($object->getFrequencyRule());
+        ->setValue($frequency);
     }
 
     if ($this->getIsCreate() || $object->getIsRecurring()) {
       $fields[] = id(new PhabricatorEpochEditField())
         ->setAllowNull(true)
         ->setKey('until')
         ->setLabel(pht('Repeat Until'))
         ->setTransactionType(
           PhabricatorCalendarEventUntilDateTransaction::TRANSACTIONTYPE)
         ->setDescription(pht('Last instance of the event.'))
         ->setConduitDescription(pht('Change when the event repeats until.'))
         ->setConduitTypeDescription(pht('New final event time.'))
         ->setValue($object->getUntilDateTimeEpoch());
     }
 
     $fields[] = id(new PhabricatorBoolEditField())
       ->setKey('isAllDay')
       ->setLabel(pht('All Day'))
       ->setOptions(pht('Normal Event'), pht('All Day Event'))
       ->setTransactionType(
         PhabricatorCalendarEventAllDayTransaction::TRANSACTIONTYPE)
       ->setDescription(pht('Marks this as an all day event.'))
       ->setConduitDescription(pht('Make the event an all day event.'))
       ->setConduitTypeDescription(pht('Mark the event as an all day event.'))
       ->setValue($object->getIsAllDay());
 
     $fields[] = id(new PhabricatorEpochEditField())
       ->setKey('start')
       ->setLabel(pht('Start'))
       ->setTransactionType(
         PhabricatorCalendarEventStartDateTransaction::TRANSACTIONTYPE)
       ->setDescription(pht('Start time of the event.'))
       ->setConduitDescription(pht('Change the start time of the event.'))
       ->setConduitTypeDescription(pht('New event start time.'))
       ->setValue($object->getStartDateTimeEpoch());
 
     $fields[] = id(new PhabricatorEpochEditField())
       ->setKey('end')
       ->setLabel(pht('End'))
       ->setTransactionType(
         PhabricatorCalendarEventEndDateTransaction::TRANSACTIONTYPE)
       ->setDescription(pht('End time of the event.'))
       ->setConduitDescription(pht('Change the end time of the event.'))
       ->setConduitTypeDescription(pht('New event end time.'))
       ->setValue($object->getEndDateTimeEpoch());
 
     $fields[] = id(new PhabricatorIconSetEditField())
       ->setKey('icon')
       ->setLabel(pht('Icon'))
       ->setIconSet(new PhabricatorCalendarIconSet())
       ->setTransactionType(
         PhabricatorCalendarEventIconTransaction::TRANSACTIONTYPE)
       ->setDescription(pht('Event icon.'))
       ->setConduitDescription(pht('Change the event icon.'))
       ->setConduitTypeDescription(pht('New event icon.'))
       ->setValue($object->getIcon());
 
     return $fields;
   }
 
   protected function willBuildEditForm($object, array $fields) {
     $all_day_field = idx($fields, 'isAllDay');
     $start_field = idx($fields, 'start');
     $end_field = idx($fields, 'end');
 
     if ($all_day_field) {
       $is_all_day = $all_day_field->getValueForTransaction();
 
       $control_ids = array();
       if ($start_field) {
         $control_ids[] = $start_field->getControlID();
       }
       if ($end_field) {
         $control_ids[] = $end_field->getControlID();
       }
 
       Javelin::initBehavior(
         'event-all-day',
         array(
           'allDayID' => $all_day_field->getControlID(),
           'controlIDs' => $control_ids,
         ));
 
     } else {
       $is_all_day = $object->getIsAllDay();
     }
 
     if ($is_all_day) {
       if ($start_field) {
         $start_field->setHideTime(true);
       }
 
       if ($end_field) {
         $end_field->setHideTime(true);
       }
     }
 
 
 
     return $fields;
   }
 }
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEvent.php b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
index 060c6fe5c5..676d85b608 100644
--- a/src/applications/calendar/storage/PhabricatorCalendarEvent.php
+++ b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
@@ -1,1062 +1,1041 @@
 <?php
 
 final class PhabricatorCalendarEvent extends PhabricatorCalendarDAO
   implements
     PhabricatorPolicyInterface,
     PhabricatorProjectInterface,
     PhabricatorMarkupInterface,
     PhabricatorApplicationTransactionInterface,
     PhabricatorSubscribableInterface,
     PhabricatorTokenReceiverInterface,
     PhabricatorDestructibleInterface,
     PhabricatorMentionableInterface,
     PhabricatorFlaggableInterface,
     PhabricatorSpacesInterface,
     PhabricatorFulltextInterface,
     PhabricatorConduitResultInterface {
 
   protected $name;
   protected $hostPHID;
   protected $description;
   protected $isCancelled;
   protected $isAllDay;
   protected $icon;
   protected $mailKey;
   protected $isStub;
 
   protected $isRecurring = 0;
-  protected $recurrenceFrequency = array();
 
   private $isGhostEvent = false;
   protected $instanceOfEventPHID;
   protected $sequenceIndex;
 
   protected $viewPolicy;
   protected $editPolicy;
 
   protected $spacePHID;
 
   protected $utcInitialEpoch;
   protected $utcUntilEpoch;
   protected $utcInstanceEpoch;
   protected $parameters = array();
 
   private $parentEvent = self::ATTACHABLE;
   private $invitees = self::ATTACHABLE;
 
   private $viewerTimezone;
 
   // TODO: DEPRECATED. Remove once we're sure the migrations worked.
   protected $allDayDateFrom;
   protected $allDayDateTo;
   protected $dateFrom;
   protected $dateTo;
   protected $recurrenceEndDate;
-
-  // Frequency Constants
-  const FREQUENCY_DAILY = 'daily';
-  const FREQUENCY_WEEKLY = 'weekly';
-  const FREQUENCY_MONTHLY = 'monthly';
-  const FREQUENCY_YEARLY = 'yearly';
+  protected $recurrenceFrequency = array();
 
   public static function initializeNewCalendarEvent(PhabricatorUser $actor) {
     $app = id(new PhabricatorApplicationQuery())
       ->setViewer($actor)
       ->withClasses(array('PhabricatorCalendarApplication'))
       ->executeOne();
 
     $view_default = PhabricatorCalendarEventDefaultViewCapability::CAPABILITY;
     $edit_default = PhabricatorCalendarEventDefaultEditCapability::CAPABILITY;
     $view_policy = $app->getPolicy($view_default);
     $edit_policy = $app->getPolicy($edit_default);
 
     $now = PhabricatorTime::getNow();
 
     $default_icon = 'fa-calendar';
 
     $datetime_start = PhutilCalendarAbsoluteDateTime::newFromEpoch(
       $now,
       $actor->getTimezoneIdentifier());
     $datetime_end = $datetime_start->newRelativeDateTime('PT1H');
 
     return id(new PhabricatorCalendarEvent())
       ->setHostPHID($actor->getPHID())
       ->setIsCancelled(0)
       ->setIsAllDay(0)
       ->setIsStub(0)
       ->setIsRecurring(0)
-      ->setRecurrenceFrequency(
-        array(
-          'rule' => self::FREQUENCY_WEEKLY,
-        ))
       ->setIcon($default_icon)
       ->setViewPolicy($view_policy)
       ->setEditPolicy($edit_policy)
       ->setSpacePHID($actor->getDefaultSpacePHID())
       ->attachInvitees(array())
       ->setDateFrom(0)
       ->setDateTo(0)
       ->setAllDayDateFrom(0)
       ->setAllDayDateTo(0)
       ->setStartDateTime($datetime_start)
       ->setEndDateTime($datetime_end)
       ->applyViewerTimezone($actor);
   }
 
   private function newChild(
     PhabricatorUser $actor,
     $sequence,
     PhutilCalendarDateTime $start = null) {
     if (!$this->isParentEvent()) {
       throw new Exception(
         pht(
           'Unable to generate a new child event for an event which is not '.
           'a recurring parent event!'));
     }
 
     $child = id(new self())
       ->setIsCancelled(0)
       ->setIsStub(0)
       ->setInstanceOfEventPHID($this->getPHID())
       ->setSequenceIndex($sequence)
       ->setIsRecurring(true)
-      ->setRecurrenceFrequency($this->getRecurrenceFrequency())
       ->attachParentEvent($this)
       ->setAllDayDateFrom(0)
       ->setAllDayDateTo(0)
       ->setDateFrom(0)
       ->setDateTo(0);
 
     return $child->copyFromParent($actor, $start);
   }
 
   protected function readField($field) {
     static $inherit = array(
       'hostPHID' => true,
       'isAllDay' => true,
       'icon' => true,
       'spacePHID' => true,
       'viewPolicy' => true,
       'editPolicy' => true,
       'name' => true,
       'description' => true,
     );
 
     // Read these fields from the parent event instead of this event. For
     // example, we want any changes to the parent event's name to apply to
     // the child.
     if (isset($inherit[$field])) {
       if ($this->getIsStub()) {
         // TODO: This should be unconditional, but the execution order of
         // CalendarEventQuery and applyViewerTimezone() are currently odd.
         if ($this->parentEvent !== self::ATTACHABLE) {
           return $this->getParentEvent()->readField($field);
         }
       }
     }
 
     return parent::readField($field);
   }
 
 
   public function copyFromParent(
     PhabricatorUser $actor,
     PhutilCalendarDateTime $start = null) {
 
     if (!$this->isChildEvent()) {
       throw new Exception(
         pht(
           'Unable to copy from parent event: this is not a child event.'));
     }
 
     $parent = $this->getParentEvent();
 
     $this
       ->setHostPHID($parent->getHostPHID())
       ->setIsAllDay($parent->getIsAllDay())
       ->setIcon($parent->getIcon())
       ->setSpacePHID($parent->getSpacePHID())
       ->setViewPolicy($parent->getViewPolicy())
       ->setEditPolicy($parent->getEditPolicy())
       ->setName($parent->getName())
       ->setDescription($parent->getDescription());
 
     $sequence = $this->getSequenceIndex();
 
     if ($start) {
       $start_datetime = $start;
     } else {
       $start_datetime = $parent->newSequenceIndexDateTime($sequence);
 
       if (!$start_datetime) {
         throw new Exception(
           pht(
             'Sequence "%s" is not valid for event!',
             $sequence));
       }
     }
 
     $duration = $parent->newDuration();
     $end_datetime = $start_datetime->newRelativeDateTime($duration);
 
     $this
       ->setStartDateTime($start_datetime)
       ->setEndDateTime($end_datetime);
 
     return $this;
   }
 
   public function isValidSequenceIndex(PhabricatorUser $viewer, $sequence) {
     return (bool)$this->newSequenceIndexDateTime($sequence);
   }
 
   public function newSequenceIndexDateTime($sequence) {
     $set = $this->newRecurrenceSet();
     if (!$set) {
       return null;
     }
 
     $instances = $set->getEventsBetween(
       null,
       $this->newUntilDateTime(),
       $sequence + 1);
 
     return idx($instances, $sequence, null);
   }
 
   public function newStub(PhabricatorUser $actor, $sequence) {
     $stub = $this->newChild($actor, $sequence);
 
     $stub->setIsStub(1);
 
     $unguarded = AphrontWriteGuard::beginScopedUnguardedWrites();
       $stub->save();
     unset($unguarded);
 
     $stub->applyViewerTimezone($actor);
 
     return $stub;
   }
 
   public function newGhost(
     PhabricatorUser $actor,
     $sequence,
     PhutilCalendarDateTime $start = null) {
 
     $ghost = $this->newChild($actor, $sequence, $start);
 
     $ghost
       ->setIsGhostEvent(true)
       ->makeEphemeral();
 
     $ghost->applyViewerTimezone($actor);
 
     return $ghost;
   }
 
   public function applyViewerTimezone(PhabricatorUser $viewer) {
     $this->viewerTimezone = $viewer->getTimezoneIdentifier();
     return $this;
   }
 
   public function getDuration() {
     return ($this->getEndDateTimeEpoch() - $this->getStartDateTimeEpoch());
   }
 
   public function updateUTCEpochs() {
     // The "intitial" epoch is the start time of the event, in UTC.
     $start_date = $this->newStartDateTime()
       ->setViewerTimezone('UTC');
     $start_epoch = $start_date->getEpoch();
     $this->setUTCInitialEpoch($start_epoch);
 
     // The "until" epoch is the last UTC epoch on which any instance of this
     // event occurs. For infinitely recurring events, it is `null`.
 
     if (!$this->getIsRecurring()) {
       $end_date = $this->newEndDateTime()
         ->setViewerTimezone('UTC');
       $until_epoch = $end_date->getEpoch();
     } else {
       $until_epoch = null;
       $until_date = $this->newUntilDateTime();
       if ($until_date) {
         $until_date->setViewerTimezone('UTC');
         $duration = $this->newDuration();
         $until_epoch = id(new PhutilCalendarRelativeDateTime())
           ->setOrigin($until_date)
           ->setDuration($duration)
           ->getEpoch();
       }
     }
     $this->setUTCUntilEpoch($until_epoch);
 
     // The "instance" epoch is a property of instances of recurring events.
     // It's the original UTC epoch on which the instance started. Usually that
     // is the same as the start date, but they may be different if the instance
     // has been edited.
 
     // The ICS format uses this value (original start time) to identify event
     // instances, and must do so because it allows additional arbitrary
     // instances to be added (with "RDATE").
 
     $instance_epoch = null;
     $instance_date = $this->newInstanceDateTime();
     if ($instance_date) {
       $instance_epoch = $instance_date
         ->setViewerTimezone('UTC')
         ->getEpoch();
     }
     $this->setUTCInstanceEpoch($instance_epoch);
 
     return $this;
   }
 
   public function save() {
     if (!$this->mailKey) {
       $this->mailKey = Filesystem::readRandomCharacters(20);
     }
 
     $this->updateUTCEpochs();
 
     return parent::save();
   }
 
   /**
    * Get the event start epoch for evaluating invitee availability.
    *
    * When assessing availability, we pretend events start earlier than they
    * really do. This allows us to mark users away for the entire duration of a
    * series of back-to-back meetings, even if they don't strictly overlap.
    *
    * @return int Event start date for availability caches.
    */
   public function getStartDateTimeEpochForCache() {
     $epoch = $this->getStartDateTimeEpoch();
     $window = phutil_units('15 minutes in seconds');
     return ($epoch - $window);
   }
 
   protected function getConfiguration() {
     return array(
       self::CONFIG_AUX_PHID => true,
       self::CONFIG_COLUMN_SCHEMA => array(
         'name' => 'text',
         'description' => 'text',
         'isCancelled' => 'bool',
         'isAllDay' => 'bool',
         'icon' => 'text32',
         'mailKey' => 'bytes20',
         'isRecurring' => 'bool',
         'instanceOfEventPHID' => 'phid?',
         'sequenceIndex' => 'uint32?',
         'isStub' => 'bool',
         'utcInitialEpoch' => 'epoch',
         'utcUntilEpoch' => 'epoch?',
         'utcInstanceEpoch' => 'epoch?',
 
         // TODO: DEPRECATED.
         'allDayDateFrom' => 'epoch',
         'allDayDateTo' => 'epoch',
         'dateFrom' => 'epoch',
         'dateTo' => 'epoch',
         'recurrenceEndDate' => 'epoch?',
       ),
       self::CONFIG_KEY_SCHEMA => array(
         'key_date' => array(
           'columns' => array('dateFrom', 'dateTo'),
         ),
         'key_instance' => array(
           'columns' => array('instanceOfEventPHID', 'sequenceIndex'),
           'unique' => true,
         ),
         'key_epoch' => array(
           'columns' => array('utcInitialEpoch', 'utcUntilEpoch'),
         ),
         'key_rdate' => array(
           'columns' => array('instanceOfEventPHID', 'utcInstanceEpoch'),
           'unique' => true,
         ),
       ),
       self::CONFIG_SERIALIZATION => array(
         'recurrenceFrequency' => self::SERIALIZATION_JSON,
         'parameters' => self::SERIALIZATION_JSON,
       ),
     ) + parent::getConfiguration();
   }
 
   public function generatePHID() {
     return PhabricatorPHID::generateNewPHID(
       PhabricatorCalendarEventPHIDType::TYPECONST);
   }
 
   public function getMonogram() {
     return 'E'.$this->getID();
   }
 
   public function getInvitees() {
     return $this->assertAttached($this->invitees);
   }
 
   public function attachInvitees(array $invitees) {
     $this->invitees = $invitees;
     return $this;
   }
 
   public function getInviteePHIDsForEdit() {
     $invitees = array();
 
     foreach ($this->getInvitees() as $invitee) {
       if ($invitee->isUninvited()) {
         continue;
       }
       $invitees[] = $invitee->getInviteePHID();
     }
 
     return $invitees;
   }
 
   public function getUserInviteStatus($phid) {
     $invitees = $this->getInvitees();
     $invitees = mpull($invitees, null, 'getInviteePHID');
 
     $invited = idx($invitees, $phid);
     if (!$invited) {
       return PhabricatorCalendarEventInvitee::STATUS_UNINVITED;
     }
     $invited = $invited->getStatus();
     return $invited;
   }
 
   public function getIsUserAttending($phid) {
     $attending_status = PhabricatorCalendarEventInvitee::STATUS_ATTENDING;
 
     $old_status = $this->getUserInviteStatus($phid);
     $is_attending = ($old_status == $attending_status);
 
     return $is_attending;
   }
 
   public function getIsUserInvited($phid) {
     $uninvited_status = PhabricatorCalendarEventInvitee::STATUS_UNINVITED;
     $declined_status = PhabricatorCalendarEventInvitee::STATUS_DECLINED;
     $status = $this->getUserInviteStatus($phid);
     if ($status == $uninvited_status || $status == $declined_status) {
       return false;
     }
     return true;
   }
 
   public function getIsGhostEvent() {
     return $this->isGhostEvent;
   }
 
   public function setIsGhostEvent($is_ghost_event) {
     $this->isGhostEvent = $is_ghost_event;
     return $this;
   }
 
-  public function getFrequencyRule() {
-    return idx($this->recurrenceFrequency, 'rule');
-  }
-
-  public function getFrequencyUnit() {
-    $frequency = $this->getFrequencyRule();
-
-    switch ($frequency) {
-      case 'daily':
-        return 'day';
-      case 'weekly':
-        return 'week';
-      case 'monthly':
-        return 'month';
-      case 'yearly':
-        return 'year';
-      default:
-        return 'day';
-    }
-  }
-
   public function getURI() {
     if ($this->getIsGhostEvent()) {
       $base = $this->getParentEvent()->getURI();
       $sequence = $this->getSequenceIndex();
       return "{$base}/{$sequence}/";
     }
 
     return '/'.$this->getMonogram();
   }
 
   public function getParentEvent() {
     return $this->assertAttached($this->parentEvent);
   }
 
   public function attachParentEvent($event) {
     $this->parentEvent = $event;
     return $this;
   }
 
   public function isParentEvent() {
     return ($this->getIsRecurring() && !$this->getInstanceOfEventPHID());
   }
 
   public function isChildEvent() {
     return ($this->instanceOfEventPHID !== null);
   }
 
   public function isCancelledEvent() {
     if ($this->getIsCancelled()) {
       return true;
     }
 
     if ($this->isChildEvent()) {
       if ($this->getParentEvent()->getIsCancelled()) {
         return true;
       }
     }
 
     return false;
   }
 
   public function renderEventDate(
     PhabricatorUser $viewer,
     $show_end) {
 
     $start = $this->newStartDateTime();
     $end = $this->newEndDateTime();
 
     if ($show_end) {
       $min_date = $start->newPHPDateTime();
       $max_date = $end->newPHPDateTime();
 
       $min_day = $min_date->format('Y m d');
       $max_day = $max_date->format('Y m d');
 
       $show_end_date = ($min_day != $max_day);
     } else {
       $show_end_date = false;
     }
 
     $min_epoch = $start->getEpoch();
     $max_epoch = $end->getEpoch();
 
     if ($this->getIsAllDay()) {
       if ($show_end_date) {
         return pht(
           '%s - %s, All Day',
           phabricator_date($min_epoch, $viewer),
           phabricator_date($max_epoch, $viewer));
       } else {
         return pht(
           '%s, All Day',
           phabricator_date($min_epoch, $viewer));
       }
     } else if ($show_end_date) {
       return pht(
         '%s - %s',
         phabricator_datetime($min_epoch, $viewer),
         phabricator_datetime($max_epoch, $viewer));
     } else if ($show_end) {
       return pht(
         '%s - %s',
         phabricator_datetime($min_epoch, $viewer),
         phabricator_time($max_epoch, $viewer));
     } else {
       return pht(
         '%s',
         phabricator_datetime($min_epoch, $viewer));
     }
   }
 
 
   public function getDisplayIcon(PhabricatorUser $viewer) {
     if ($this->isCancelledEvent()) {
       return 'fa-times';
     }
 
     if ($viewer->isLoggedIn()) {
       $status = $this->getUserInviteStatus($viewer->getPHID());
       switch ($status) {
         case PhabricatorCalendarEventInvitee::STATUS_ATTENDING:
           return 'fa-check-circle';
         case PhabricatorCalendarEventInvitee::STATUS_INVITED:
           return 'fa-user-plus';
         case PhabricatorCalendarEventInvitee::STATUS_DECLINED:
           return 'fa-times';
       }
     }
 
     return $this->getIcon();
   }
 
   public function getDisplayIconColor(PhabricatorUser $viewer) {
     if ($this->isCancelledEvent()) {
       return 'red';
     }
 
     if ($viewer->isLoggedIn()) {
       $status = $this->getUserInviteStatus($viewer->getPHID());
       switch ($status) {
         case PhabricatorCalendarEventInvitee::STATUS_ATTENDING:
           return 'green';
         case PhabricatorCalendarEventInvitee::STATUS_INVITED:
           return 'green';
         case PhabricatorCalendarEventInvitee::STATUS_DECLINED:
           return 'grey';
       }
     }
 
     return 'bluegrey';
   }
 
   public function getDisplayIconLabel(PhabricatorUser $viewer) {
     if ($this->isCancelledEvent()) {
       return pht('Cancelled');
     }
 
     if ($viewer->isLoggedIn()) {
       $status = $this->getUserInviteStatus($viewer->getPHID());
       switch ($status) {
         case PhabricatorCalendarEventInvitee::STATUS_ATTENDING:
           return pht('Attending');
         case PhabricatorCalendarEventInvitee::STATUS_INVITED:
           return pht('Invited');
         case PhabricatorCalendarEventInvitee::STATUS_DECLINED:
           return pht('Declined');
       }
     }
 
     return null;
   }
 
   public function getICSFilename() {
     return $this->getMonogram().'.ics';
   }
 
   public function newIntermediateEventNode(PhabricatorUser $viewer) {
     $base_uri = new PhutilURI(PhabricatorEnv::getProductionURI('/'));
     $domain = $base_uri->getDomain();
 
     $uid = $this->getPHID().'@'.$domain;
 
     $created = $this->getDateCreated();
     $created = PhutilCalendarAbsoluteDateTime::newFromEpoch($created);
 
     $modified = $this->getDateModified();
     $modified = PhutilCalendarAbsoluteDateTime::newFromEpoch($modified);
 
     $date_start = $this->newStartDateTime();
     $date_end = $this->newEndDateTime();
 
     if ($this->getIsAllDay()) {
       $date_start->setIsAllDay(true);
       $date_end->setIsAllDay(true);
     }
 
     $host_phid = $this->getHostPHID();
 
     $invitees = $this->getInvitees();
     foreach ($invitees as $key => $invitee) {
       if ($invitee->isUninvited()) {
         unset($invitees[$key]);
       }
     }
 
     $phids = array();
     $phids[] = $host_phid;
     foreach ($invitees as $invitee) {
       $phids[] = $invitee->getInviteePHID();
     }
 
     $handles = $viewer->loadHandles($phids);
 
     $host_handle = $handles[$host_phid];
     $host_name = $host_handle->getFullName();
     $host_uri = $host_handle->getURI();
     $host_uri = PhabricatorEnv::getURI($host_uri);
 
     $organizer = id(new PhutilCalendarUserNode())
       ->setName($host_name)
       ->setURI($host_uri);
 
     $attendees = array();
     foreach ($invitees as $invitee) {
       $invitee_phid = $invitee->getInviteePHID();
       $invitee_handle = $handles[$invitee_phid];
       $invitee_name = $invitee_handle->getFullName();
       $invitee_uri = $invitee_handle->getURI();
       $invitee_uri = PhabricatorEnv::getURI($invitee_uri);
 
       switch ($invitee->getStatus()) {
         case PhabricatorCalendarEventInvitee::STATUS_ATTENDING:
           $status = PhutilCalendarUserNode::STATUS_ACCEPTED;
           break;
         case PhabricatorCalendarEventInvitee::STATUS_DECLINED:
           $status = PhutilCalendarUserNode::STATUS_DECLINED;
           break;
         case PhabricatorCalendarEventInvitee::STATUS_INVITED:
         default:
           $status = PhutilCalendarUserNode::STATUS_INVITED;
           break;
       }
 
       $attendees[] = id(new PhutilCalendarUserNode())
         ->setName($invitee_name)
         ->setURI($invitee_uri)
         ->setStatus($status);
     }
 
     $node = id(new PhutilCalendarEventNode())
       ->setUID($uid)
       ->setName($this->getName())
       ->setDescription($this->getDescription())
       ->setCreatedDateTime($created)
       ->setModifiedDateTime($modified)
       ->setStartDateTime($date_start)
       ->setEndDateTime($date_end)
       ->setOrganizer($organizer)
       ->setAttendees($attendees);
 
     return $node;
   }
 
   public function newStartDateTime() {
     $datetime = $this->getParameter('startDateTime');
     if ($datetime) {
       return $this->newDateTimeFromDictionary($datetime);
     }
 
     $epoch = $this->getDateFrom();
     return $this->newDateTimeFromEpoch($epoch);
   }
 
   public function getStartDateTimeEpoch() {
     return $this->newStartDateTime()->getEpoch();
   }
 
   public function newEndDateTime() {
     $datetime = $this->getParameter('endDateTime');
     if ($datetime) {
       return $this->newDateTimeFromDictionary($datetime);
     }
 
     $epoch = $this->getDateTo();
     return $this->newDateTimeFromEpoch($epoch);
   }
 
   public function getEndDateTimeEpoch() {
     return $this->newEndDateTime()->getEpoch();
   }
 
   public function newUntilDateTime() {
     $datetime = $this->getParameter('untilDateTime');
     if ($datetime) {
       return $this->newDateTimeFromDictionary($datetime);
     }
 
     $epoch = $this->getRecurrenceEndDate();
     if (!$epoch) {
       return null;
     }
     return $this->newDateTimeFromEpoch($epoch);
   }
 
   public function getUntilDateTimeEpoch() {
     $datetime = $this->newUntilDateTime();
 
     if (!$datetime) {
       return null;
     }
 
     return $datetime->getEpoch();
   }
 
   public function newDuration() {
     return id(new PhutilCalendarDuration())
       ->setSeconds($this->getDuration());
   }
 
   public function newInstanceDateTime() {
     if (!$this->getIsRecurring()) {
       return null;
     }
 
     $index = $this->getSequenceIndex();
     if (!$index) {
       return null;
     }
 
     return $this->newSequenceIndexDateTime($index);
   }
 
   private function newDateTimeFromEpoch($epoch) {
     $datetime = PhutilCalendarAbsoluteDateTime::newFromEpoch($epoch);
 
     if ($this->getIsAllDay()) {
       $datetime->setIsAllDay(true);
     }
 
     return $this->newDateTimeFromDateTime($datetime);
   }
 
   private function newDateTimeFromDictionary(array $dict) {
     $datetime = PhutilCalendarAbsoluteDateTime::newFromDictionary($dict);
     return $this->newDateTimeFromDateTime($datetime);
   }
 
   private function newDateTimeFromDateTime(PhutilCalendarDateTime $datetime) {
     $viewer_timezone = $this->viewerTimezone;
     if ($viewer_timezone) {
       $datetime->setViewerTimezone($viewer_timezone);
     }
 
     return $datetime;
   }
 
   public function getParameter($key, $default = null) {
     return idx($this->parameters, $key, $default);
   }
 
   public function setParameter($key, $value) {
     $this->parameters[$key] = $value;
     return $this;
   }
 
   public function setStartDateTime(PhutilCalendarDateTime $datetime) {
     return $this->setParameter(
       'startDateTime',
       $datetime->newAbsoluteDateTime()->toDictionary());
   }
 
   public function setEndDateTime(PhutilCalendarDateTime $datetime) {
     return $this->setParameter(
       'endDateTime',
       $datetime->newAbsoluteDateTime()->toDictionary());
   }
 
   public function setUntilDateTime(PhutilCalendarDateTime $datetime) {
     return $this->setParameter(
       'untilDateTime',
       $datetime->newAbsoluteDateTime()->toDictionary());
   }
 
+  public function setRecurrenceRule(PhutilCalendarRecurrenceRule $rrule) {
+    return $this->setParameter(
+      'recurrenceRule',
+      $rrule->toDictionary());
+  }
 
   public function newRecurrenceRule() {
     if ($this->isChildEvent()) {
       return $this->getParentEvent()->newRecurrenceRule();
     }
 
-    // TODO: This is a little fragile since it relies on the convenient
-    // definition of FREQUENCY constants here and in RecurrenceRule, but
-    // should be gone soon.
-    $map = array(
-      'FREQ' => phutil_utf8_strtoupper($this->getFrequencyRule()),
-    );
+    if (!$this->getIsRecurring()) {
+      return null;
+    }
+
+    $dict = $this->getParameter('recurrenceRule');
+    if (!$dict) {
+      return null;
+    }
 
-    $rrule = PhutilCalendarRecurrenceRule::newFromDictionary($map);
+    $rrule = PhutilCalendarRecurrenceRule::newFromDictionary($dict);
 
     $start = $this->newStartDateTime();
     $rrule->setStartDateTime($start);
 
     return $rrule;
   }
 
   public function newRecurrenceSet() {
     if ($this->isChildEvent()) {
       return $this->getParentEvent()->newRecurrenceSet();
     }
 
     $set = new PhutilCalendarRecurrenceSet();
 
     $rrule = $this->newRecurrenceRule();
+    if (!$rrule) {
+      return null;
+    }
+
     $set->addSource($rrule);
 
     return $set;
   }
 
 /* -(  Markup Interface  )--------------------------------------------------- */
 
 
   /**
    * @task markup
    */
   public function getMarkupFieldKey($field) {
     $hash = PhabricatorHash::digest($this->getMarkupText($field));
     $id = $this->getID();
     return "calendar:T{$id}:{$field}:{$hash}";
   }
 
 
   /**
    * @task markup
    */
   public function getMarkupText($field) {
     return $this->getDescription();
   }
 
 
   /**
    * @task markup
    */
   public function newMarkupEngine($field) {
     return PhabricatorMarkupEngine::newCalendarMarkupEngine();
   }
 
 
   /**
    * @task markup
    */
   public function didMarkupText(
     $field,
     $output,
     PhutilMarkupEngine $engine) {
     return $output;
   }
 
 
   /**
    * @task markup
    */
   public function shouldUseMarkupCache($field) {
     return (bool)$this->getID();
   }
 
 /* -(  PhabricatorPolicyInterface  )----------------------------------------- */
 
 
   public function getCapabilities() {
     return array(
       PhabricatorPolicyCapability::CAN_VIEW,
       PhabricatorPolicyCapability::CAN_EDIT,
     );
   }
 
   public function getPolicy($capability) {
     switch ($capability) {
       case PhabricatorPolicyCapability::CAN_VIEW:
         return $this->getViewPolicy();
       case PhabricatorPolicyCapability::CAN_EDIT:
         return $this->getEditPolicy();
     }
   }
 
   public function hasAutomaticCapability($capability, PhabricatorUser $viewer) {
     // The host of an event can always view and edit it.
     $user_phid = $this->getHostPHID();
     if ($user_phid) {
       $viewer_phid = $viewer->getPHID();
       if ($viewer_phid == $user_phid) {
         return true;
       }
     }
 
     if ($capability == PhabricatorPolicyCapability::CAN_VIEW) {
       $status = $this->getUserInviteStatus($viewer->getPHID());
       if ($status == PhabricatorCalendarEventInvitee::STATUS_INVITED ||
         $status == PhabricatorCalendarEventInvitee::STATUS_ATTENDING ||
         $status == PhabricatorCalendarEventInvitee::STATUS_DECLINED) {
         return true;
       }
     }
 
     return false;
   }
 
   public function describeAutomaticCapability($capability) {
     return pht(
       'The host of an event can always view and edit it. Users who are '.
       'invited to an event can always view it.');
   }
 
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */
 
 
   public function getApplicationTransactionEditor() {
     return new PhabricatorCalendarEventEditor();
   }
 
   public function getApplicationTransactionObject() {
     return $this;
   }
 
   public function getApplicationTransactionTemplate() {
     return new PhabricatorCalendarEventTransaction();
   }
 
   public function willRenderTimeline(
     PhabricatorApplicationTransactionView $timeline,
     AphrontRequest $request) {
 
     return $timeline;
   }
 
 /* -(  PhabricatorSubscribableInterface  )----------------------------------- */
 
 
   public function isAutomaticallySubscribed($phid) {
     return ($phid == $this->getHostPHID());
   }
 
 /* -(  PhabricatorTokenReceiverInterface  )---------------------------------- */
 
 
   public function getUsersToNotifyOfTokenGiven() {
     return array($this->getHostPHID());
   }
 
 /* -(  PhabricatorDestructibleInterface  )----------------------------------- */
 
 
   public function destroyObjectPermanently(
     PhabricatorDestructionEngine $engine) {
 
     $this->openTransaction();
     $this->delete();
     $this->saveTransaction();
   }
 
 /* -(  PhabricatorSpacesInterface  )----------------------------------------- */
 
 
   public function getSpacePHID() {
     return $this->spacePHID;
   }
 
 
 /* -(  PhabricatorFulltextInterface  )--------------------------------------- */
 
 
   public function newFulltextEngine() {
     return new PhabricatorCalendarEventFulltextEngine();
   }
 
 
 /* -(  PhabricatorConduitResultInterface  )---------------------------------- */
 
 
   public function getFieldSpecificationsForConduit() {
     return array(
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('name')
         ->setType('string')
         ->setDescription(pht('The name of the event.')),
       id(new PhabricatorConduitSearchFieldSpecification())
         ->setKey('description')
         ->setType('string')
         ->setDescription(pht('The event description.')),
     );
   }
 
   public function getFieldValuesForConduit() {
     return array(
       'name' => $this->getName(),
       'description' => $this->getDescription(),
     );
   }
 
   public function getConduitSearchAttachments() {
     return array();
   }
 
 }
diff --git a/src/applications/calendar/xaction/PhabricatorCalendarEventFrequencyTransaction.php b/src/applications/calendar/xaction/PhabricatorCalendarEventFrequencyTransaction.php
index 9690a97dce..2da4f1da62 100644
--- a/src/applications/calendar/xaction/PhabricatorCalendarEventFrequencyTransaction.php
+++ b/src/applications/calendar/xaction/PhabricatorCalendarEventFrequencyTransaction.php
@@ -1,75 +1,115 @@
 <?php
 
 final class PhabricatorCalendarEventFrequencyTransaction
   extends PhabricatorCalendarEventTransactionType {
 
   const TRANSACTIONTYPE = 'calendar.frequency';
 
   public function generateOldValue($object) {
-    return $object->getFrequencyRule();
+    $rrule = $object->newRecurrenceRule();
+
+    if (!$rrule) {
+      return null;
+    }
+
+    return $rrule->getFrequency();
   }
 
   public function applyInternalEffects($object, $value) {
-    $object->setRecurrenceFrequency(
-      array(
-        'rule' => $value,
-      ));
+    $rrule = id(new PhutilCalendarRecurrenceRule())
+      ->setFrequency($value);
+
+    $dict = $rrule->toDictionary();
+    $object->setRecurrenceRule($dict);
+  }
+
+  public function validateTransactions($object, array $xactions) {
+    $errors = array();
+
+    $valid = array(
+      PhutilCalendarRecurrenceRule::FREQUENCY_DAILY,
+      PhutilCalendarRecurrenceRule::FREQUENCY_WEEKLY,
+      PhutilCalendarRecurrenceRule::FREQUENCY_MONTHLY,
+      PhutilCalendarRecurrenceRule::FREQUENCY_YEARLY,
+    );
+    $valid = array_fuse($valid);
+
+    foreach ($xactions as $xaction) {
+      $value = $xaction->getNewValue();
+
+      if (!isset($valid[$value])) {
+        $errors[] = $this->newInvalidError(
+          pht(
+            'Event frequency "%s" is not valid. Valid frequences are: %s.',
+            $value,
+            implode(', ', $valid)),
+          $xaction);
+      }
+    }
+
+    return $errors;
   }
 
   public function getTitle() {
-    $frequency = $this->getFrequencyRule($this->getNewValue());
+    $frequency = $this->getFrequency($this->getNewValue());
     switch ($frequency) {
-      case PhabricatorCalendarEvent::FREQUENCY_DAILY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_DAILY:
         return pht(
           '%s set this event to repeat daily.',
           $this->renderAuthor());
-      case PhabricatorCalendarEvent::FREQUENCY_WEEKLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_WEEKLY:
         return pht(
           '%s set this event to repeat weekly.',
           $this->renderAuthor());
-      case PhabricatorCalendarEvent::FREQUENCY_MONTHLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_MONTHLY:
         return pht(
           '%s set this event to repeat monthly.',
           $this->renderAuthor());
-      case PhabricatorCalendarEvent::FREQUENCY_YEARLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_YEARLY:
         return pht(
           '%s set this event to repeat yearly.',
           $this->renderAuthor());
     }
   }
 
   public function getTitleForFeed() {
-    $frequency = $this->getFrequencyRule($this->getNewValue());
+    $frequency = $this->getFrequency($this->getNewValue());
     switch ($frequency) {
-      case PhabricatorCalendarEvent::FREQUENCY_DAILY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_DAILY:
         return pht(
           '%s set %s to repeat daily.',
           $this->renderAuthor(),
           $this->renderObject());
-      case PhabricatorCalendarEvent::FREQUENCY_WEEKLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_WEEKLY:
         return pht(
           '%s set %s to repeat weekly.',
           $this->renderAuthor(),
           $this->renderObject());
-      case PhabricatorCalendarEvent::FREQUENCY_MONTHLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_MONTHLY:
         return pht(
           '%s set %s to repeat monthly.',
           $this->renderAuthor(),
           $this->renderObject());
-      case PhabricatorCalendarEvent::FREQUENCY_YEARLY:
+      case PhutilCalendarRecurrenceRule::FREQUENCY_YEARLY:
         return pht(
           '%s set %s to repeat yearly.',
           $this->renderAuthor(),
           $this->renderObject());
     }
   }
 
-  private function getFrequencyRule($value) {
+  private function getFrequency($value) {
+    // NOTE: This is normalizing three generations of these transactions
+    // to use RRULE constants. It would be vaguely nice to migrate them
+    // for consistency.
+
     if (is_array($value)) {
       $value = idx($value, 'rule');
     } else {
-      return $value;
+      $value = $value;
     }
+
+    return phutil_utf8_strtoupper($value);
   }
 
 }