diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index ad88264ee5..422fee0b9d 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -331,7 +331,8 @@ return array(
     'rsrc/js/application/aphlict/behavior-aphlict-listen.js' => 'b1a59974',
     'rsrc/js/application/aphlict/behavior-aphlict-status.js' => 'ea681761',
     'rsrc/js/application/auth/behavior-persona-login.js' => '9414ff18',
-    'rsrc/js/application/calendar/event-all-day.js' => 'ca5fa62a',
+    'rsrc/js/application/calendar/behavior-day-view.js' => 'f4f4ad80',
+    'rsrc/js/application/calendar/behavior-event-all-day.js' => '38dcf3c8',
     'rsrc/js/application/config/behavior-reorder-fields.js' => '14a827de',
     'rsrc/js/application/conpherence/ConpherenceThreadManager.js' => '10246726',
     'rsrc/js/application/conpherence/behavior-drag-and-drop-photo.js' => 'cf86d16a',
@@ -553,6 +554,7 @@ return array(
     'javelin-behavior-dashboard-move-panels' => '82439934',
     'javelin-behavior-dashboard-query-panel-select' => '453c5375',
     'javelin-behavior-dashboard-tab-panel' => 'd4eecc63',
+    'javelin-behavior-day-view' => 'f4f4ad80',
     'javelin-behavior-device' => 'a205cf28',
     'javelin-behavior-differential-add-reviewers-and-ccs' => 'e10f8e18',
     'javelin-behavior-differential-comment-jump' => '4fdb476d',
@@ -573,7 +575,7 @@ return array(
     'javelin-behavior-doorkeeper-tag' => 'e5822781',
     'javelin-behavior-durable-column' => '16c695bf',
     'javelin-behavior-error-log' => '6882e80a',
-    'javelin-behavior-event-all-day' => 'ca5fa62a',
+    'javelin-behavior-event-all-day' => '38dcf3c8',
     'javelin-behavior-fancy-datepicker' => '5c0f680f',
     'javelin-behavior-global-drag-and-drop' => 'c8e57404',
     'javelin-behavior-herald-rule-editor' => '7ebaeed3',
diff --git a/src/view/phui/calendar/PHUICalendarDayView.php b/src/view/phui/calendar/PHUICalendarDayView.php
index 337ef50738..7a96100b2a 100644
--- a/src/view/phui/calendar/PHUICalendarDayView.php
+++ b/src/view/phui/calendar/PHUICalendarDayView.php
@@ -10,6 +10,7 @@ final class PHUICalendarDayView extends AphrontView {
   private $browseURI;
   private $events = array();
   private $todayEvents = array();
+  private $jsTodayEvents = array();
 
   private $allDayEvents = array();
 
@@ -45,6 +46,7 @@ final class PHUICalendarDayView extends AphrontView {
     require_celerity_resource('phui-calendar-day-css');
 
     $hours = $this->getHoursOfDay();
+    $js_hourly_events = array();
     $hourly_events = array();
 
     $first_event_hour = null;
@@ -83,6 +85,11 @@ final class PHUICalendarDayView extends AphrontView {
           && $event->getEpochStart() < $hour_end)) {
           $current_hour_events[] = $event;
           $this->todayEvents[] = $event;
+          $this->jsTodayEvents[] = array(
+            'eventStartEpoch' => $event->getEpochStart(),
+            'eventEndEpoch' => $event->getEpochEnd(),
+            'eventName' => $event->getName(),
+          );
         }
       }
       foreach ($current_hour_events as $event) {
@@ -102,6 +109,17 @@ final class PHUICalendarDayView extends AphrontView {
           $first_event_hour = $hour;
         }
 
+        $js_hourly_events[$event->getEventID()] = array(
+          'eventStartEpoch' => $event->getEpochStart(),
+          'eventEndEpoch' => $event->getEpochEnd(),
+          'eventName' => $event->getName(),
+          'hour' => $hour,
+          'offset' => '0',
+          'width' => '100%',
+          'top' => $top.'%',
+          'height' => $height.'%',
+        );
+
         $hourly_events[$event->getEventID()] = array(
           'hour' => $hour,
           'event' => $event,
@@ -176,6 +194,13 @@ final class PHUICalendarDayView extends AphrontView {
     $sidebar = $this->renderSidebar();
     $warnings = $this->getQueryRangeWarning();
 
+    Javelin::initBehavior(
+      'day-view',
+      array(
+        'todayEvents' => $this->jsTodayEvents,
+        'hourlyEvents' => $js_hourly_events,
+      ));
+
     $table_box = id(new PHUIObjectBoxView())
       ->setHeader($header)
       ->appendChild($all_day_event_box)
diff --git a/webroot/rsrc/js/application/calendar/behavior-day-view.js b/webroot/rsrc/js/application/calendar/behavior-day-view.js
new file mode 100644
index 0000000000..9cd90e01bc
--- /dev/null
+++ b/webroot/rsrc/js/application/calendar/behavior-day-view.js
@@ -0,0 +1,50 @@
+/**
+ * @provides javelin-behavior-day-view
+ */
+
+
+JX.behavior('day-view', function(config) {
+  var hourly_events = config.hourlyEvents;
+  var today_events = config.todayEvents;
+
+  function findTodayClusters() {
+    var events = today_events.sort(function(x, y){
+      return (x.eventStartEpoch - y.eventStartEpoch);
+    });
+
+    var clusters = [];
+
+    events.forEach(function(e){
+      var destination_cluster_index = null;
+      var event_start = e.eventStartEpoch - (30*60);
+      var event_end = e.eventEndEpoch + (30*60);
+
+      clusters.forEach(function(cluster, index){
+        for(var i=0; i < cluster.length; i++) {
+          var clustered_event = cluster[i];
+          var compare_event_start = clustered_event.eventStartEpoch;
+          var compare_event_end = clustered_event.eventEndEpoch;
+
+          if (event_start < compare_event_end &&
+            event_end > compare_event_start) {
+            destination_cluster_index = index;
+            break;
+          }
+        }
+      });
+
+      if (destination_cluster_index !== null) {
+        clusters[destination_cluster_index].push(e);
+        destination_cluster_index = null;
+      } else {
+        var next_cluster = [];
+        next_cluster.push(e);
+        clusters.push(next_cluster);
+      }
+    });
+
+    return clusters;
+  }
+
+  var today_clusters = findTodayClusters();
+});
diff --git a/webroot/rsrc/js/application/calendar/event-all-day.js b/webroot/rsrc/js/application/calendar/behavior-event-all-day.js
similarity index 100%
rename from webroot/rsrc/js/application/calendar/event-all-day.js
rename to webroot/rsrc/js/application/calendar/behavior-event-all-day.js