diff --git a/src/applications/phrequent/storage/PhrequentTimeSlices.php b/src/applications/phrequent/storage/PhrequentTimeSlices.php
index 30c4345720..b19f857149 100644
--- a/src/applications/phrequent/storage/PhrequentTimeSlices.php
+++ b/src/applications/phrequent/storage/PhrequentTimeSlices.php
@@ -1,37 +1,39 @@
 <?php
 
 final class PhrequentTimeSlices extends Phobject {
 
   private $objectPHID;
   private $isOngoing;
   private $ranges;
 
   public function __construct($object_phid, $is_ongoing, array $ranges) {
     $this->objectPHID = $object_phid;
     $this->isOngoing = $is_ongoing;
     $this->ranges = $ranges;
   }
 
   public function getObjectPHID() {
     return $this->objectPHID;
   }
 
   public function getDuration($now) {
+    $total = 0;
     foreach ($this->ranges as $range) {
       if ($range[1] === null) {
-        return $now - $range[0];
+        $total += $now - $range[0];
       } else {
-        return $range[1] - $range[0];
+        $total += $range[1] - $range[0];
       }
     }
+    return $total;
   }
 
   public function getIsOngoing() {
     return $this->isOngoing;
   }
 
   public function getRanges() {
     return $this->ranges;
   }
 
 }
diff --git a/src/applications/phrequent/storage/__tests__/PhrequentTimeBlockTestCase.php b/src/applications/phrequent/storage/__tests__/PhrequentTimeBlockTestCase.php
index d42560090e..b2e062a8e8 100644
--- a/src/applications/phrequent/storage/__tests__/PhrequentTimeBlockTestCase.php
+++ b/src/applications/phrequent/storage/__tests__/PhrequentTimeBlockTestCase.php
@@ -1,305 +1,329 @@
 <?php
 
 final class PhrequentTimeBlockTestCase extends PhabricatorTestCase {
 
   public function testMergeTimeRanges() {
 
     // Overlapping ranges.
     $input = array(
       array(50, 150),
       array(100, 175),
     );
     $expect = array(
       array(50, 175),
     );
 
     $this->assertEqual($expect, PhrequentTimeBlock::mergeTimeRanges($input));
 
 
     // Identical ranges.
     $input = array(
       array(1, 1),
       array(1, 1),
       array(1, 1),
     );
     $expect = array(
       array(1, 1),
     );
 
     $this->assertEqual($expect, PhrequentTimeBlock::mergeTimeRanges($input));
 
 
     // Range which is a strict subset of another range.
     $input = array(
       array(2, 7),
       array(1, 10),
     );
     $expect = array(
       array(1, 10),
     );
 
     $this->assertEqual($expect, PhrequentTimeBlock::mergeTimeRanges($input));
 
 
     // These are discontinuous and should not be merged.
     $input = array(
       array(5, 6),
       array(7, 8),
     );
     $expect = array(
       array(5, 6),
       array(7, 8),
     );
 
     $this->assertEqual($expect, PhrequentTimeBlock::mergeTimeRanges($input));
 
 
     // These overlap only on an edge, but should merge.
     $input = array(
       array(5, 6),
       array(6, 7),
     );
     $expect = array(
       array(5, 7),
     );
 
     $this->assertEqual($expect, PhrequentTimeBlock::mergeTimeRanges($input));
   }
 
   public function testPreemptingEvents() {
 
     // Roughly, this is: got into work, started T1, had a meeting from 10-11,
     // left the office around 2 to meet a client at a coffee shop, worked on
     // T1 again for about 40 minutes, had the meeting from 3-3:30, finished up
     // on T1, headed back to the office, got another hour of work in, and
     // headed home.
 
     $event = $this->newEvent('T1', 900, 1700);
 
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('meeting', 1000, 1100),
         $this->newEvent('offsite', 1400, 1600),
         $this->newEvent('T1', 1420, 1580),
         $this->newEvent('offsite meeting', 1500, 1550),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(900, 1000),  // Before morning meeting.
           array(1100, 1400), // After morning meeting.
           array(1420, 1500), // Coffee, before client meeting.
           array(1550, 1580), // Coffee, after client meeting.
           array(1600, 1700), // After returning from off site.
         ),
       ),
       $ranges);
 
     $event = $this->newEvent('T2', 100, 300);
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('meeting', 200, null),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T2' => array(
           array(100, 200),
         ),
       ),
       $ranges);
   }
 
   public function testTimelineSort() {
     $e1 = $this->newEvent('X1', 1, 1)->setID(1);
 
     $in = array(
       array(
         'event' => $e1,
         'at' => 1,
         'type' => 'start',
       ),
       array(
         'event' => $e1,
         'at' => 1,
         'type' => 'end',
       ),
     );
 
     usort($in, array('PhrequentTimeBlock', 'sortTimeline'));
 
     $this->assertEqual(
       array(
         'start',
         'end',
       ),
       ipull($in, 'type'));
   }
 
   public function testInstantaneousEvent() {
 
     $event = $this->newEvent('T1', 8, 8);
     $event->attachPreemptingEvents(array());
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(8, 8),
         ),
       ),
       $ranges);
   }
 
   public function testPopAcrossStrata() {
 
     $event = $this->newEvent('T1', 1, 1000);
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('T2', 100, 300),
         $this->newEvent('T1', 200, 400),
         $this->newEvent('T3', 250, 275),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(1, 100),
           array(200, 250),
           array(275, 1000),
         ),
       ),
       $ranges);
   }
 
   public function testEndDeeperStratum() {
     $event = $this->newEvent('T1', 1, 1000);
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('T2', 100, 900),
         $this->newEvent('T1', 200, 400),
         $this->newEvent('T3', 300, 800),
         $this->newEvent('T1', 350, 600),
         $this->newEvent('T4', 380, 390),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(1, 100),
           array(200, 300),
           array(350, 380),
           array(390, 600),
           array(900, 1000),
         ),
       ),
       $ranges);
   }
 
   public function testOngoing() {
     $event = $this->newEvent('T1', 1, null);
     $event->attachPreemptingEvents(array());
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(1, null),
         ),
       ),
       $ranges);
   }
 
   public function testOngoingInterrupted() {
     $event = $this->newEvent('T1', 1, null);
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('T2', 100, 900),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(1, 100),
           array(900, null)
         ),
       ),
       $ranges);
   }
 
   public function testOngoingPreempted() {
     $event = $this->newEvent('T1', 1, null);
     $event->attachPreemptingEvents(
       array(
         $this->newEvent('T2', 100, null),
       ));
 
     $block = new PhrequentTimeBlock(array($event));
 
     $ranges = $block->getObjectTimeRanges();
     $ranges = $this->reduceRanges($ranges);
 
     $this->assertEqual(
       array(
         'T1' => array(
           array(1, 100),
         ),
       ),
       $ranges);
   }
 
+  public function testSumTimeSlices() {
+    // This block has multiple closed slices.
+    $block = new PhrequentTimeBlock(
+      array(
+        $this->newEvent('T1', 3456, 4456)->attachPreemptingEvents(array()),
+        $this->newEvent('T1', 8000, 9000)->attachPreemptingEvents(array()),
+      ));
+
+    $this->assertEqual(
+      2000,
+      $block->getTimeSpentOnObject('T1', 10000));
+
+    // This block has an open slice.
+    $block = new PhrequentTimeBlock(
+      array(
+        $this->newEvent('T1', 3456, 4456)->attachPreemptingEvents(array()),
+        $this->newEvent('T1', 8000, null)->attachPreemptingEvents(array()),
+      ));
+
+    $this->assertEqual(
+      3000,
+      $block->getTimeSpentOnObject('T1', 10000));
+  }
+
   private function newEvent($object_phid, $start_time, $end_time) {
     static $id = 0;
 
     return id(new PhrequentUserTime())
       ->setID(++$id)
       ->setObjectPHID($object_phid)
       ->setDateStarted($start_time)
       ->setDateEnded($end_time);
   }
 
   private function reduceRanges(array $ranges) {
     $results = array();
 
     foreach ($ranges as $phid => $slices) {
       $results[$phid] = $slices->getRanges();
     }
 
     return $results;
   }
 
 }