diff --git a/src/applications/fact/chart/PhabricatorChartDataset.php b/src/applications/fact/chart/PhabricatorChartDataset.php
--- a/src/applications/fact/chart/PhabricatorChartDataset.php
+++ b/src/applications/fact/chart/PhabricatorChartDataset.php
@@ -59,13 +59,6 @@
     return $dataset;
   }
 
-  final public function toDictionary() {
-    return array(
-      'type' => $this->getDatasetTypeKey(),
-      'functions' => mpull($this->getFunctions(), 'toDictionary'),
-    );
-  }
-
   final public function getChartDisplayData(
     PhabricatorChartDataQuery $data_query) {
     return $this->newChartDisplayData($data_query);
diff --git a/src/applications/fact/chart/PhabricatorChartFunction.php b/src/applications/fact/chart/PhabricatorChartFunction.php
--- a/src/applications/fact/chart/PhabricatorChartFunction.php
+++ b/src/applications/fact/chart/PhabricatorChartFunction.php
@@ -60,6 +60,10 @@
     return $this->functionLabel;
   }
 
+  final public function getKey() {
+    return $this->getFunctionLabel()->getKey();
+  }
+
   final public static function newFromDictionary(array $map) {
     PhutilTypeSpec::checkMap(
       $map,
@@ -86,13 +90,6 @@
     return $function;
   }
 
-  public function toDictionary() {
-    return array(
-      'function' => $this->getFunctionKey(),
-      'arguments' => $this->getArgumentParser()->getRawArguments(),
-    );
-  }
-
   public function getSubfunctions() {
     $result = array();
     $result[] = $this;
diff --git a/src/applications/fact/chart/PhabricatorChartFunctionLabel.php b/src/applications/fact/chart/PhabricatorChartFunctionLabel.php
--- a/src/applications/fact/chart/PhabricatorChartFunctionLabel.php
+++ b/src/applications/fact/chart/PhabricatorChartFunctionLabel.php
@@ -3,11 +3,21 @@
 final class PhabricatorChartFunctionLabel
   extends Phobject {
 
+  private $key;
   private $name;
   private $color;
   private $icon;
   private $fillColor;
 
+  public function setKey($key) {
+    $this->key = $key;
+    return $this;
+  }
+
+  public function getKey() {
+    return $this->key;
+  }
+
   public function setName($name) {
     $this->name = $name;
     return $this;
@@ -46,6 +56,7 @@
 
   public function toWireFormat() {
     return array(
+      'key' => $this->getKey(),
       'name' => $this->getName(),
       'color' => $this->getColor(),
       'icon' => $this->getIcon(),
diff --git a/src/applications/fact/chart/PhabricatorChartStackedAreaDataset.php b/src/applications/fact/chart/PhabricatorChartStackedAreaDataset.php
--- a/src/applications/fact/chart/PhabricatorChartStackedAreaDataset.php
+++ b/src/applications/fact/chart/PhabricatorChartStackedAreaDataset.php
@@ -5,124 +5,89 @@
 
   const DATASETKEY = 'stacked-area';
 
-  protected function newChartDisplayData(
-    PhabricatorChartDataQuery $data_query) {
-    $functions = $this->getFunctions();
+  private $stacks;
 
-    $reversed_functions = array_reverse($functions, true);
+  public function setStacks(array $stacks) {
+    $this->stacks = $stacks;
+    return $this;
+  }
 
-    $function_points = array();
-    foreach ($reversed_functions as $function_idx => $function) {
-      $function_points[$function_idx] = array();
+  public function getStacks() {
+    return $this->stacks;
+  }
 
-      $datapoints = $function->newDatapoints($data_query);
-      foreach ($datapoints as $point) {
-        $x_value = $point['x'];
-        $function_points[$function_idx][$x_value] = $point;
-      }
-    }
+  protected function newChartDisplayData(
+    PhabricatorChartDataQuery $data_query) {
 
-    $raw_points = $function_points;
+    $functions = $this->getFunctions();
+    $functions = mpull($functions, null, 'getKey');
 
-    // We need to define every function we're drawing at every point where
-    // any of the functions we're drawing are defined. If we don't, we'll
-    // end up with weird gaps or overlaps between adjacent areas, and won't
-    // know how much we need to lift each point above the baseline when
-    // stacking the functions on top of one another.
+    $stacks = $this->getStacks();
 
-    $must_define = array();
-    foreach ($function_points as $function_idx => $points) {
-      foreach ($points as $x => $point) {
-        $must_define[$x] = $x;
-      }
+    if (!$stacks) {
+      $stacks = array(
+        array_reverse(array_keys($functions), true),
+      );
     }
-    ksort($must_define);
 
-    foreach ($reversed_functions as $function_idx => $function) {
-      $missing = array();
-      foreach ($must_define as $x) {
-        if (!isset($function_points[$function_idx][$x])) {
-          $missing[$x] = true;
+    $series = array();
+    $raw_points = array();
+
+    foreach ($stacks as $stack) {
+      $stack_functions = array_select_keys($functions, $stack);
+
+      $function_points = $this->getFunctionDatapoints(
+        $data_query,
+        $stack_functions);
+
+      $stack_points = $function_points;
+
+      $function_points = $this->getGeometry(
+        $data_query,
+        $function_points);
+
+      $baseline = array();
+      foreach ($function_points as $function_idx => $points) {
+        $bounds = array();
+        foreach ($points as $x => $point) {
+          if (!isset($baseline[$x])) {
+            $baseline[$x] = 0;
+          }
+
+          $y0 = $baseline[$x];
+          $baseline[$x] += $point['y'];
+          $y1 = $baseline[$x];
+
+          $bounds[] = array(
+            'x' => $x,
+            'y0' => $y0,
+            'y1' => $y1,
+          );
+
+          if (isset($stack_points[$function_idx][$x])) {
+            $stack_points[$function_idx][$x]['y1'] = $y1;
+          }
         }
-      }
 
-      if (!$missing) {
-        continue;
+        $series[$function_idx] = $bounds;
       }
 
-      $points = $function_points[$function_idx];
-
-      $values = array_keys($points);
-      $cursor = -1;
-      $length = count($values);
-
-      foreach ($missing as $x => $ignored) {
-        // Move the cursor forward until we find the last point before "x"
-        // which is defined.
-        while ($cursor + 1 < $length && $values[$cursor + 1] < $x) {
-          $cursor++;
-        }
-
-        // If this new point is to the left of all defined points, we'll
-        // assume the value is 0. If the point is to the right of all defined
-        // points, we assume the value is the same as the last known value.
-
-        // If it's between two defined points, we average them.
-
-        if ($cursor < 0) {
-          $y = 0;
-        } else if ($cursor + 1 < $length) {
-          $xmin = $values[$cursor];
-          $xmax = $values[$cursor + 1];
-
-          $ymin = $points[$xmin]['y'];
-          $ymax = $points[$xmax]['y'];
-
-          // Fill in the missing point by creating a linear interpolation
-          // between the two adjacent points.
-          $distance = ($x - $xmin) / ($xmax - $xmin);
-          $y = $ymin + (($ymax - $ymin) * $distance);
-        } else {
-          $xmin = $values[$cursor];
-          $y = $function_points[$function_idx][$xmin]['y'];
-        }
+      $raw_points += $stack_points;
+    }
 
-        $function_points[$function_idx][$x] = array(
-          'x' => $x,
-          'y' => $y,
-        );
-      }
+    $series = array_select_keys($series, array_keys($functions));
+    $series = array_values($series);
 
-      ksort($function_points[$function_idx]);
-    }
+    $raw_points = array_select_keys($raw_points, array_keys($functions));
+    $raw_points = array_values($raw_points);
 
     $range_min = null;
     $range_max = null;
 
-    $series = array();
-    $baseline = array();
-    foreach ($function_points as $function_idx => $points) {
-      $below = idx($function_points, $function_idx - 1);
-
-      $bounds = array();
-      foreach ($points as $x => $point) {
-        if (!isset($baseline[$x])) {
-          $baseline[$x] = 0;
-        }
-
-        $y0 = $baseline[$x];
-        $baseline[$x] += $point['y'];
-        $y1 = $baseline[$x];
-
-        $bounds[] = array(
-          'x' => $x,
-          'y0' => $y0,
-          'y1' => $y1,
-        );
-
-        if (isset($raw_points[$function_idx][$x])) {
-          $raw_points[$function_idx][$x]['y1'] = $y1;
-        }
+    foreach ($series as $geometry_list) {
+      foreach ($geometry_list as $geometry_item) {
+        $y0 = $geometry_item['y0'];
+        $y1 = $geometry_item['y1'];
 
         if ($range_min === null) {
           $range_min = $y0;
@@ -134,12 +99,8 @@
         }
         $range_max = max($range_max, $y0, $y1);
       }
-
-      $series[] = $bounds;
     }
 
-    $series = array_reverse($series);
-
     // We're going to group multiple events into a single point if they have
     // X values that are very close to one another.
     //
@@ -222,5 +183,118 @@
       ->setRange(new PhabricatorChartInterval($range_min, $range_max));
   }
 
+  private function getAllXValuesAsMap(
+    PhabricatorChartDataQuery $data_query,
+    array $point_lists) {
+
+    // We need to define every function we're drawing at every point where
+    // any of the functions we're drawing are defined. If we don't, we'll
+    // end up with weird gaps or overlaps between adjacent areas, and won't
+    // know how much we need to lift each point above the baseline when
+    // stacking the functions on top of one another.
+
+    $must_define = array();
+
+    $min = $data_query->getMinimumValue();
+    $max = $data_query->getMaximumValue();
+    $must_define[$max] = $max;
+    $must_define[$min] = $min;
+
+    foreach ($point_lists as $point_list) {
+      foreach ($point_list as $x => $point) {
+        $must_define[$x] = $x;
+      }
+    }
+
+    ksort($must_define);
+
+    return $must_define;
+  }
+
+  private function getFunctionDatapoints(
+    PhabricatorChartDataQuery $data_query,
+    array $functions) {
+
+    assert_instances_of($functions, 'PhabricatorChartFunction');
+
+    $points = array();
+    foreach ($functions as $idx => $function) {
+      $points[$idx] = array();
+
+      $datapoints = $function->newDatapoints($data_query);
+      foreach ($datapoints as $point) {
+        $x_value = $point['x'];
+        $points[$idx][$x_value] = $point;
+      }
+    }
+
+    return $points;
+  }
+
+  private function getGeometry(
+    PhabricatorChartDataQuery $data_query,
+    array $point_lists) {
+
+    $must_define = $this->getAllXValuesAsMap($data_query, $point_lists);
+
+    foreach ($point_lists as $idx => $points) {
+
+      $missing = array();
+      foreach ($must_define as $x) {
+        if (!isset($points[$x])) {
+          $missing[$x] = true;
+        }
+      }
+
+      if (!$missing) {
+        continue;
+      }
+
+      $values = array_keys($points);
+      $cursor = -1;
+      $length = count($values);
+
+      foreach ($missing as $x => $ignored) {
+        // Move the cursor forward until we find the last point before "x"
+        // which is defined.
+        while ($cursor + 1 < $length && $values[$cursor + 1] < $x) {
+          $cursor++;
+        }
+
+        // If this new point is to the left of all defined points, we'll
+        // assume the value is 0. If the point is to the right of all defined
+        // points, we assume the value is the same as the last known value.
+
+        // If it's between two defined points, we average them.
+
+        if ($cursor < 0) {
+          $y = 0;
+        } else if ($cursor + 1 < $length) {
+          $xmin = $values[$cursor];
+          $xmax = $values[$cursor + 1];
+
+          $ymin = $points[$xmin]['y'];
+          $ymax = $points[$xmax]['y'];
+
+          // Fill in the missing point by creating a linear interpolation
+          // between the two adjacent points.
+          $distance = ($x - $xmin) / ($xmax - $xmin);
+          $y = $ymin + (($ymax - $ymin) * $distance);
+        } else {
+          $xmin = $values[$cursor];
+          $y = $points[$xmin]['y'];
+        }
+
+        $point_lists[$idx][$x] = array(
+          'x' => $x,
+          'y' => $y,
+        );
+      }
+
+      ksort($point_lists[$idx]);
+    }
+
+    return $point_lists;
+  }
 
 }
diff --git a/src/applications/project/chart/PhabricatorProjectBurndownChartEngine.php b/src/applications/project/chart/PhabricatorProjectBurndownChartEngine.php
--- a/src/applications/project/chart/PhabricatorProjectBurndownChartEngine.php
+++ b/src/applications/project/chart/PhabricatorProjectBurndownChartEngine.php
@@ -29,6 +29,8 @@
     }
 
     $functions = array();
+    $stacks = array();
+
     if ($project_phids) {
       foreach ($project_phids as $project_phid) {
         $function = $this->newFunction(
@@ -42,12 +44,31 @@
           ));
 
         $function->getFunctionLabel()
+          ->setKey('moved-in')
           ->setName(pht('Tasks Moved Into Project'))
           ->setColor('rgba(128, 128, 200, 1)')
           ->setFillColor('rgba(128, 128, 200, 0.15)');
 
         $functions[] = $function;
 
+        $function = $this->newFunction(
+          array(
+            'accumulate',
+            array(
+              'compose',
+              array('fact', 'tasks.open-count.status.project', $project_phid),
+              array('min', 0),
+            ),
+          ));
+
+        $function->getFunctionLabel()
+          ->setKey('reopened')
+          ->setName(pht('Tasks Reopened'))
+          ->setColor('rgba(128, 128, 200, 1)')
+          ->setFillColor('rgba(128, 128, 200, 0.15)');
+
+        $functions[] = $function;
+
         $function = $this->newFunction(
           array(
             'accumulate',
@@ -55,6 +76,7 @@
           ));
 
         $function->getFunctionLabel()
+          ->setKey('created')
           ->setName(pht('Tasks Created'))
           ->setColor('rgba(0, 0, 200, 1)')
           ->setFillColor('rgba(0, 0, 200, 0.15)');
@@ -66,30 +88,39 @@
             'accumulate',
             array(
               'compose',
-              array('fact', 'tasks.open-count.assign.project', $project_phid),
+              array('fact', 'tasks.open-count.status.project', $project_phid),
               array('max', 0),
             ),
           ));
 
         $function->getFunctionLabel()
-          ->setName(pht('Tasks Moved Out of Project'))
-          ->setColor('rgba(128, 200, 128, 1)')
-          ->setFillColor('rgba(128, 200, 128, 0.15)');
+          ->setKey('closed')
+          ->setName(pht('Tasks Closed'))
+          ->setColor('rgba(0, 200, 0, 1)')
+          ->setFillColor('rgba(0, 200, 0, 0.15)');
 
         $functions[] = $function;
 
         $function = $this->newFunction(
           array(
             'accumulate',
-            array('fact', 'tasks.open-count.status.project', $project_phid),
+            array(
+              'compose',
+              array('fact', 'tasks.open-count.assign.project', $project_phid),
+              array('max', 0),
+            ),
           ));
 
         $function->getFunctionLabel()
-          ->setName(pht('Tasks Closed'))
-          ->setColor('rgba(0, 200, 0, 1)')
-          ->setFillColor('rgba(0, 200, 0, 0.15)');
+          ->setKey('moved-out')
+          ->setName(pht('Tasks Moved Out of Project'))
+          ->setColor('rgba(128, 200, 128, 1)')
+          ->setFillColor('rgba(128, 200, 128, 0.15)');
 
         $functions[] = $function;
+
+        $stacks[] = array('created', 'reopened', 'moved-in');
+        $stacks[] = array('closed', 'moved-out');
       }
     } else {
       $function = $this->newFunction(
@@ -99,7 +130,8 @@
         ));
 
       $function->getFunctionLabel()
-        ->setName(pht('Tasks Created'))
+        ->setKey('open')
+        ->setName(pht('Open Tasks'))
         ->setColor('rgba(0, 0, 200, 1)')
         ->setFillColor('rgba(0, 0, 200, 0.15)');
 
@@ -112,7 +144,8 @@
         ));
 
       $function->getFunctionLabel()
-        ->setName(pht('Tasks Closed'))
+        ->setKey('closed')
+        ->setName(pht('Closed Tasks'))
         ->setColor('rgba(0, 200, 0, 1)')
         ->setFillColor('rgba(0, 200, 0, 0.15)');
 
@@ -121,9 +154,14 @@
 
     $datasets = array();
 
-    $datasets[] = id(new PhabricatorChartStackedAreaDataset())
+    $dataset = id(new PhabricatorChartStackedAreaDataset())
       ->setFunctions($functions);
 
+    if ($stacks) {
+      $dataset->setStacks($stacks);
+    }
+
+    $datasets[] = $dataset;
     $chart->attachDatasets($datasets);
   }