diff --git a/resources/sql/autopatches/20150427.calendar.1.xaction.sql b/resources/sql/autopatches/20150427.calendar.1.xaction.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20150427.calendar.1.xaction.sql
@@ -0,0 +1,19 @@
+CREATE TABLE {$NAMESPACE}_calendar.calendar_eventtransaction (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  phid VARBINARY(64) NOT NULL,
+  authorPHID VARBINARY(64) NOT NULL,
+  objectPHID VARBINARY(64) NOT NULL,
+  viewPolicy VARBINARY(64) NOT NULL,
+  editPolicy VARBINARY(64) NOT NULL,
+  commentPHID VARBINARY(64) DEFAULT NULL,
+  commentVersion INT UNSIGNED NOT NULL,
+  transactionType VARCHAR(32) COLLATE {$COLLATE_TEXT} NOT NULL,
+  oldValue LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  newValue LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  contentSource LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  metadata LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  dateCreated INT UNSIGNED NOT NULL,
+  dateModified INT UNSIGNED NOT NULL,
+  UNIQUE KEY `key_phid` (`phid`),
+  KEY `key_object` (`objectPHID`)
+) ENGINE=InnoDB, COLLATE {$COLLATE_TEXT};
diff --git a/resources/sql/autopatches/20150427.calendar.2.xaction.sql b/resources/sql/autopatches/20150427.calendar.2.xaction.sql
new file mode 100644
--- /dev/null
+++ b/resources/sql/autopatches/20150427.calendar.2.xaction.sql
@@ -0,0 +1,16 @@
+CREATE TABLE {$NAMESPACE}_calendar.calendar_eventtransaction_comment (
+  id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
+  phid VARBINARY(64) NOT NULL,
+  transactionPHID VARBINARY(64) DEFAULT NULL,
+  authorPHID VARBINARY(64) NOT NULL,
+  viewPolicy VARBINARY(64) NOT NULL,
+  editPolicy VARBINARY(64) NOT NULL,
+  commentVersion INT UNSIGNED NOT NULL,
+  content LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  contentSource LONGTEXT COLLATE {$COLLATE_TEXT} NOT NULL,
+  isDeleted TINYINT(1) NOT NULL,
+  dateCreated INT UNSIGNED NOT NULL,
+  dateModified INT UNSIGNED NOT NULL,
+  UNIQUE KEY `key_phid` (`phid`),
+  UNIQUE KEY `key_version` (`transactionPHID`,`commentVersion`)
+) ENGINE=InnoDB COLLATE {$COLLATE_TEXT}
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -1484,11 +1484,15 @@
     'PhabricatorCalendarEvent' => 'applications/calendar/storage/PhabricatorCalendarEvent.php',
     'PhabricatorCalendarEventDeleteController' => 'applications/calendar/controller/PhabricatorCalendarEventDeleteController.php',
     'PhabricatorCalendarEventEditController' => 'applications/calendar/controller/PhabricatorCalendarEventEditController.php',
+    'PhabricatorCalendarEventEditor' => 'applications/calendar/editor/PhabricatorCalendarEventEditor.php',
     'PhabricatorCalendarEventInvalidEpochException' => 'applications/calendar/exception/PhabricatorCalendarEventInvalidEpochException.php',
     'PhabricatorCalendarEventListController' => 'applications/calendar/controller/PhabricatorCalendarEventListController.php',
     'PhabricatorCalendarEventPHIDType' => 'applications/calendar/phid/PhabricatorCalendarEventPHIDType.php',
     'PhabricatorCalendarEventQuery' => 'applications/calendar/query/PhabricatorCalendarEventQuery.php',
     'PhabricatorCalendarEventSearchEngine' => 'applications/calendar/query/PhabricatorCalendarEventSearchEngine.php',
+    'PhabricatorCalendarEventTransaction' => 'applications/calendar/storage/PhabricatorCalendarEventTransaction.php',
+    'PhabricatorCalendarEventTransactionComment' => 'applications/calendar/storage/PhabricatorCalendarEventTransactionComment.php',
+    'PhabricatorCalendarEventTransactionQuery' => 'applications/calendar/query/PhabricatorCalendarEventTransactionQuery.php',
     'PhabricatorCalendarEventViewController' => 'applications/calendar/controller/PhabricatorCalendarEventViewController.php',
     'PhabricatorCalendarHoliday' => 'applications/calendar/storage/PhabricatorCalendarHoliday.php',
     'PhabricatorCalendarHolidayTestCase' => 'applications/calendar/storage/__tests__/PhabricatorCalendarHolidayTestCase.php',
@@ -4802,14 +4806,19 @@
       'PhabricatorCalendarDAO',
       'PhabricatorPolicyInterface',
       'PhabricatorMarkupInterface',
+      'PhabricatorApplicationTransactionInterface',
     ),
     'PhabricatorCalendarEventDeleteController' => 'PhabricatorCalendarController',
     'PhabricatorCalendarEventEditController' => 'PhabricatorCalendarController',
+    'PhabricatorCalendarEventEditor' => 'PhabricatorApplicationTransactionEditor',
     'PhabricatorCalendarEventInvalidEpochException' => 'Exception',
     'PhabricatorCalendarEventListController' => 'PhabricatorCalendarController',
     'PhabricatorCalendarEventPHIDType' => 'PhabricatorPHIDType',
     'PhabricatorCalendarEventQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
     'PhabricatorCalendarEventSearchEngine' => 'PhabricatorApplicationSearchEngine',
+    'PhabricatorCalendarEventTransaction' => 'PhabricatorApplicationTransaction',
+    'PhabricatorCalendarEventTransactionComment' => 'PhabricatorApplicationTransactionComment',
+    'PhabricatorCalendarEventTransactionQuery' => 'PhabricatorApplicationTransactionQuery',
     'PhabricatorCalendarEventViewController' => 'PhabricatorCalendarController',
     'PhabricatorCalendarHoliday' => 'PhabricatorCalendarDAO',
     'PhabricatorCalendarHolidayTestCase' => 'PhabricatorTestCase',
diff --git a/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php b/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
--- a/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
+++ b/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
@@ -30,13 +30,13 @@
       ->setInitialTime(AphrontFormDateControl::TIME_END_OF_DAY);
 
     if ($this->isCreate()) {
-      $status       = new PhabricatorCalendarEvent();
-      $end_value    = $end_time->readValueFromRequest($request);
-      $start_value  = $start_time->readValueFromRequest($request);
+      $status = PhabricatorCalendarEvent::initializeNewCalendarEvent($user);
+      $end_value = $end_time->readValueFromRequest($request);
+      $start_value = $start_time->readValueFromRequest($request);
       $submit_label = pht('Create');
-      $filter       = 'status/create/';
-      $page_title   = pht('Create Event');
-      $redirect     = 'created';
+      $filter = 'status/create/';
+      $page_title = pht('Create Event');
+      $redirect = 'created';
     } else {
       $status = id(new PhabricatorCalendarEventQuery())
         ->setViewer($user)
@@ -61,6 +61,7 @@
 
     $errors = array();
     if ($request->isFormPost()) {
+      $xactions    = array();
       $type        = $request->getInt('status');
       $start_value = $start_time->readValueFromRequest($request);
       $end_value   = $end_time->readValueFromRequest($request);
@@ -73,39 +74,33 @@
         $errors[] = pht('Invalid end time; reset to default.');
       }
       if (!$errors) {
-        try {
-          $status
-            ->setUserPHID($user->getPHID())
-            ->setStatus($type)
-            ->setDateFrom($start_value)
-            ->setDateTo($end_value)
-            ->setDescription($description)
-            ->save();
-        } catch (PhabricatorCalendarEventInvalidEpochException $e) {
-          $errors[] = pht('Start must be before end.');
-        }
-      }
-
-      if (!$errors) {
-        $uri = new PhutilURI($this->getApplicationURI());
-        $uri->setQueryParams(
-          array(
-            'month'   => phabricator_format_local_time($status->getDateFrom(),
-                                                       $user,
-                                                       'm'),
-            'year'    => phabricator_format_local_time($status->getDateFrom(),
-                                                       $user,
-                                                       'Y'),
-            $redirect => true,
-          ));
-        if ($request->isAjax()) {
-          $response = id(new AphrontAjaxResponse())
-            ->setContent(array('redirect_uri' => $uri));
-        } else {
-          $response = id(new AphrontRedirectResponse())
-            ->setURI($uri);
-        }
-        return $response;
+        $xactions[] = id(new PhabricatorCalendarEventTransaction())
+          ->setTransactionType(
+            PhabricatorCalendarEventTransaction::TYPE_START_DATE)
+          ->setNewValue($start_value);
+
+        $xactions[] = id(new PhabricatorCalendarEventTransaction())
+          ->setTransactionType(
+            PhabricatorCalendarEventTransaction::TYPE_END_DATE)
+          ->setNewValue($end_value);
+
+        $xactions[] = id(new PhabricatorCalendarEventTransaction())
+          ->setTransactionType(
+            PhabricatorCalendarEventTransaction::TYPE_STATUS)
+          ->setNewValue($type);
+
+        $xactions[] = id(new PhabricatorCalendarEventTransaction())
+          ->setTransactionType(
+            PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION)
+          ->setNewValue($description);
+
+        $editor = id(new PhabricatorCalendarEventEditor())
+          ->setActor($user)
+          ->setContentSourceFromRequest($request)
+          ->setContinueOnNoEffect(true);
+
+        $xactions = $editor->applyTransactions($status, $xactions);
+        return id(new AphrontRedirectResponse())->setURI('/E'.$status->getID());
       }
     }
 
diff --git a/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php b/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
--- a/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
+++ b/src/applications/calendar/controller/PhabricatorCalendarEventViewController.php
@@ -29,6 +29,10 @@
     $crumbs = $this->buildApplicationCrumbs();
     $crumbs->addTextCrumb($title, '/E'.$event->getID());
 
+    $timeline = $this->buildTransactionTimeline(
+      $event,
+      new PhabricatorCalendarEventTransactionQuery());
+
     $header = $this->buildHeaderView($event);
     $actions = $this->buildActionView($event);
     $properties = $this->buildPropertyView($event);
@@ -42,6 +46,7 @@
       array(
         $crumbs,
         $box,
+        $timeline,
       ),
       array(
         'title' => $title,
diff --git a/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php b/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/editor/PhabricatorCalendarEventEditor.php
@@ -0,0 +1,108 @@
+<?php
+
+final class PhabricatorCalendarEventEditor
+  extends PhabricatorApplicationTransactionEditor {
+
+  public function getEditorApplicationClass() {
+    return 'PhabricatorCalendarApplication';
+  }
+
+  public function getEditorObjectsDescription() {
+    return pht('Calendar');
+  }
+
+  public function getTransactionTypes() {
+    $types = parent::getTransactionTypes();
+
+    $types[] = PhabricatorCalendarEventTransaction::TYPE_START_DATE;
+    $types[] = PhabricatorCalendarEventTransaction::TYPE_END_DATE;
+    $types[] = PhabricatorCalendarEventTransaction::TYPE_STATUS;
+    $types[] = PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION;
+
+    $types[] = PhabricatorTransactions::TYPE_VIEW_POLICY;
+    $types[] = PhabricatorTransactions::TYPE_EDIT_POLICY;
+
+    return $types;
+  }
+
+  protected function getCustomTransactionOldValue(
+    PhabricatorLiskDAO $object,
+    PhabricatorApplicationTransaction $xaction) {
+    switch ($xaction->getTransactionType()) {
+      case PhabricatorCalendarEventTransaction::TYPE_START_DATE:
+        return $object->getDateFrom();
+      case PhabricatorCalendarEventTransaction::TYPE_END_DATE:
+        return $object->getDateTo();
+      case PhabricatorCalendarEventTransaction::TYPE_STATUS:
+        $status = $object->getStatus();
+        if ($status === null) {
+          return null;
+        }
+        return (int)$status;
+      case PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION:
+        return $object->getDescription();
+    }
+
+    return parent::getCustomTransactionOldValue($object, $xaction);
+  }
+
+  protected function getCustomTransactionNewValue(
+    PhabricatorLiskDAO $object,
+    PhabricatorApplicationTransaction $xaction) {
+
+    switch ($xaction->getTransactionType()) {
+      case PhabricatorCalendarEventTransaction::TYPE_START_DATE:
+      case PhabricatorCalendarEventTransaction::TYPE_END_DATE:
+      case PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION:
+        return $xaction->getNewValue();
+      case PhabricatorCalendarEventTransaction::TYPE_STATUS:
+        return (int)$xaction->getNewValue();
+    }
+
+    return parent::getCustomTransactionNewValue($object, $xaction);
+  }
+
+  protected function applyCustomInternalTransaction(
+    PhabricatorLiskDAO $object,
+    PhabricatorApplicationTransaction $xaction) {
+
+    switch ($xaction->getTransactionType()) {
+      case PhabricatorCalendarEventTransaction::TYPE_START_DATE:
+        $object->setDateFrom($xaction->getNewValue());
+        return;
+      case PhabricatorCalendarEventTransaction::TYPE_END_DATE:
+        $object->setDateTo($xaction->getNewValue());
+        return;
+      case PhabricatorCalendarEventTransaction::TYPE_STATUS:
+        $object->setStatus($xaction->getNewValue());
+        return;
+      case PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION:
+        $object->setDescription($xaction->getNewValue());
+        return;
+      case PhabricatorTransactions::TYPE_VIEW_POLICY:
+      case PhabricatorTransactions::TYPE_EDIT_POLICY:
+      case PhabricatorTransactions::TYPE_EDGE:
+        return;
+    }
+
+    return parent::applyCustomInternalTransaction($object, $xaction);
+  }
+
+  protected function applyCustomExternalTransaction(
+    PhabricatorLiskDAO $object,
+    PhabricatorApplicationTransaction $xaction) {
+
+    switch ($xaction->getTransactionType()) {
+      case PhabricatorCalendarEventTransaction::TYPE_START_DATE:
+      case PhabricatorCalendarEventTransaction::TYPE_END_DATE:
+      case PhabricatorCalendarEventTransaction::TYPE_STATUS:
+      case PhabricatorCalendarEventTransaction::TYPE_DESCRIPTION:
+      case PhabricatorTransactions::TYPE_VIEW_POLICY:
+      case PhabricatorTransactions::TYPE_EDIT_POLICY:
+      case PhabricatorTransactions::TYPE_EDGE:
+        return;
+    }
+
+    return parent::applyCustomExternalTransaction($object, $xaction);
+  }
+}
diff --git a/src/applications/calendar/query/PhabricatorCalendarEventTransactionQuery.php b/src/applications/calendar/query/PhabricatorCalendarEventTransactionQuery.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/query/PhabricatorCalendarEventTransactionQuery.php
@@ -0,0 +1,10 @@
+<?php
+
+final class PhabricatorCalendarEventTransactionQuery
+  extends PhabricatorApplicationTransactionQuery {
+
+  public function getTemplateApplicationTransaction() {
+    return new PhabricatorCalendarEventTransaction();
+  }
+
+}
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEvent.php b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
--- a/src/applications/calendar/storage/PhabricatorCalendarEvent.php
+++ b/src/applications/calendar/storage/PhabricatorCalendarEvent.php
@@ -2,7 +2,8 @@
 
 final class PhabricatorCalendarEvent extends PhabricatorCalendarDAO
   implements PhabricatorPolicyInterface,
-  PhabricatorMarkupInterface {
+  PhabricatorMarkupInterface,
+  PhabricatorApplicationTransactionInterface {
 
   protected $userPHID;
   protected $dateFrom;
@@ -13,6 +14,16 @@
   const STATUS_AWAY = 1;
   const STATUS_SPORADIC = 2;
 
+  public static function initializeNewCalendarEvent(PhabricatorUser $actor) {
+    $app = id(new PhabricatorApplicationQuery())
+      ->setViewer($actor)
+      ->withClasses(array('PhabricatorCalendarApplication'))
+      ->executeOne();
+
+    return id(new PhabricatorCalendarEvent())
+      ->setUserPHID($actor->getPHID());
+  }
+
   private static $statusTexts = array(
     self::STATUS_AWAY => 'away',
     self::STATUS_SPORADIC => 'sporadic',
@@ -86,6 +97,17 @@
     return mpull($statuses, null, 'getUserPHID');
   }
 
+  public static function getNameForStatus($value) {
+    switch ($value) {
+      case self::STATUS_AWAY:
+        return pht('Away');
+      case self::STATUS_SPORADIC:
+        return pht('Sporadic');
+      default:
+        return pht('Unknown');
+    }
+  }
+
   /**
    * Validates data and throws exceptions for non-sensical status
    * windows
@@ -173,4 +195,26 @@
     return null;
   }
 
+/* -(  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;
+  }
+
 }
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php b/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/storage/PhabricatorCalendarEventTransaction.php
@@ -0,0 +1,210 @@
+<?php
+
+final class PhabricatorCalendarEventTransaction
+  extends PhabricatorApplicationTransaction {
+
+  const TYPE_START_DATE = 'calendar.startdate';
+  const TYPE_END_DATE = 'calendar.enddate';
+  const TYPE_STATUS = 'calendar.status';
+  const TYPE_DESCRIPTION = 'calendar.description';
+
+  const MAILTAG_CONTENT = 'calendar-content';
+  const MAILTAG_OTHER = 'calendar-other';
+
+  public function getApplicationName() {
+    return 'calendar';
+  }
+
+  public function getApplicationTransactionType() {
+    return PhabricatorCalendarEventPHIDType::TYPECONST;
+  }
+
+  public function getApplicationTransactionCommentObject() {
+    return new PhabricatorCalendarEventTransactionComment();
+  }
+
+  public function getRequiredHandlePHIDs() {
+    $phids = parent::getRequiredHandlePHIDs();
+
+    switch ($this->getTransactionType()) {
+      case self::TYPE_START_DATE:
+      case self::TYPE_END_DATE:
+      case self::TYPE_STATUS:
+      case self::TYPE_DESCRIPTION:
+        $phids[] = $this->getObjectPHID();
+        break;
+    }
+
+    return $phids;
+  }
+
+  public function shouldHide() {
+    $old = $this->getOldValue();
+    switch ($this->getTransactionType()) {
+      case self::TYPE_START_DATE:
+      case self::TYPE_END_DATE:
+      case self::TYPE_STATUS:
+      case self::TYPE_DESCRIPTION:
+        return ($old === null);
+    }
+    return parent::shouldHide();
+  }
+
+  public function getIcon() {
+    switch ($this->getTransactionType()) {
+      case self::TYPE_START_DATE:
+      case self::TYPE_END_DATE:
+      case self::TYPE_STATUS:
+      case self::TYPE_DESCRIPTION:
+        return 'fa-pencil';
+        break;
+    }
+    return parent::getIcon();
+  }
+
+  public function getTitle() {
+    $author_phid = $this->getAuthorPHID();
+    $object_phid = $this->getObjectPHID();
+
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    $type = $this->getTransactionType();
+    switch ($type) {
+      case self::TYPE_START_DATE:
+        if ($old) {
+          return pht(
+            '%s edited the start date of this event.',
+            $this->renderHandleLink($author_phid));
+        }
+        break;
+      case self::TYPE_END_DATE:
+        if ($old) {
+          return pht(
+            '%s edited the end date of this event.',
+            $this->renderHandleLink($author_phid));
+        }
+        break;
+      case self::TYPE_STATUS:
+        $old_name = PhabricatorCalendarEvent::getNameForStatus($old);
+        $new_name = PhabricatorCalendarEvent::getNameForStatus($new);
+        return pht(
+          '%s updated the event status from %s to %s.',
+          $this->renderHandleLink($author_phid),
+          $old_name,
+          $new_name);
+        break;
+      case self::TYPE_DESCRIPTION:
+        return pht(
+          "%s updated the event's description.",
+          $this->renderHandleLink($author_phid));
+        break;
+    }
+
+    return parent::getTitle();
+  }
+
+  public function getTitleForFeed() {
+    $author_phid = $this->getAuthorPHID();
+    $object_phid = $this->getObjectPHID();
+
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    $type = $this->getTransactionType();
+    switch ($type) {
+      case self::TYPE_START_DATE:
+        if ($old) {
+          return pht(
+            '%s edited the start date of this event from %s to %s.',
+            $this->renderHandleLink($author_phid),
+            $old,
+            $new);
+        }
+        break;
+      case self::TYPE_END_DATE:
+        if ($old) {
+          return pht(
+            '%s edited the end date of this event from %s to %s.',
+            $this->renderHandleLink($author_phid),
+            $old,
+            $new);
+        }
+        break;
+      case self::TYPE_STATUS:
+        return pht(
+          '%s updated the event status from %s to %s.',
+          $this->renderHandleLink($author_phid),
+          $old,
+          $new);
+        break;
+      case self::TYPE_DESCRIPTION:
+        return pht(
+          "%s updated the event's description.",
+          $this->renderHandleLink($author_phid));
+        break;
+    }
+
+    return parent::getTitleForFeed();
+  }
+
+  public function getColor() {
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    switch ($this->getTransactionType()) {
+      case self::TYPE_START_DATE:
+      case self::TYPE_END_DATE:
+      case self::TYPE_STATUS:
+      case self::TYPE_DESCRIPTION:
+        return PhabricatorTransactions::COLOR_GREEN;
+    }
+
+    return parent::getColor();
+  }
+
+
+  public function hasChangeDetails() {
+    switch ($this->getTransactionType()) {
+      case self::TYPE_DESCRIPTION:
+        return ($this->getOldValue() !== null);
+    }
+
+    return parent::hasChangeDetails();
+  }
+
+  public function renderChangeDetails(PhabricatorUser $viewer) {
+    switch ($this->getTransactionType()) {
+      case self::TYPE_DESCRIPTION:
+        $old = $this->getOldValue();
+        $new = $this->getNewValue();
+
+        return $this->renderTextCorpusChangeDetails(
+          $viewer,
+          $old,
+          $new);
+    }
+
+    return parent::renderChangeDetails($viewer);
+  }
+
+  public function getMailTags() {
+    $tags = array();
+    switch ($this->getTransactionType()) {
+      case self::TYPE_START_DATE:
+        $tags[] = self::MAILTAG_CONTENT;
+        break;
+      case self::TYPE_END_DATE:
+        $tags[] = self::MAILTAG_CONTENT;
+        break;
+      case self::TYPE_STATUS:
+        $tags[] = self::MAILTAG_OTHER;
+        break;
+      case self::TYPE_DESCRIPTION:
+        $tags[] = self::MAILTAG_CONTENT;
+        break;
+    }
+    return $tags;
+  }
+
+}
diff --git a/src/applications/calendar/storage/PhabricatorCalendarEventTransactionComment.php b/src/applications/calendar/storage/PhabricatorCalendarEventTransactionComment.php
new file mode 100644
--- /dev/null
+++ b/src/applications/calendar/storage/PhabricatorCalendarEventTransactionComment.php
@@ -0,0 +1,10 @@
+<?php
+
+final class PhabricatorCalendarEventTransactionComment
+  extends PhabricatorApplicationTransactionComment {
+
+  public function getApplicationTransactionObject() {
+    return new PhabricatorCalendarEventTransaction();
+  }
+
+}