diff --git a/resources/celerity/map.php b/resources/celerity/map.php
index c0bc1bf629..54832d23ae 100644
--- a/resources/celerity/map.php
+++ b/resources/celerity/map.php
@@ -484,7 +484,7 @@ return array(
     'rsrc/js/core/behavior-device.js' => 'bb1dd507',
     'rsrc/js/core/behavior-drag-and-drop-textarea.js' => '484a6e22',
     'rsrc/js/core/behavior-error-log.js' => '6882e80a',
-    'rsrc/js/core/behavior-fancy-datepicker.js' => 'a9210d03',
+    'rsrc/js/core/behavior-fancy-datepicker.js' => 'ecf4e799',
     'rsrc/js/core/behavior-file-tree.js' => '88236f00',
     'rsrc/js/core/behavior-form.js' => '5c54cbf3',
     'rsrc/js/core/behavior-gesture.js' => '3ab51e2c',
@@ -633,7 +633,7 @@ return array(
     'javelin-behavior-editengine-reorder-fields' => 'b59e1e96',
     'javelin-behavior-error-log' => '6882e80a',
     'javelin-behavior-event-all-day' => 'b41537c9',
-    'javelin-behavior-fancy-datepicker' => 'a9210d03',
+    'javelin-behavior-fancy-datepicker' => 'ecf4e799',
     'javelin-behavior-global-drag-and-drop' => '960f6a39',
     'javelin-behavior-herald-rule-editor' => '7ebaeed3',
     'javelin-behavior-high-security-warning' => 'a464fe03',
@@ -1716,13 +1716,6 @@ return array(
       'javelin-uri',
       'phabricator-keyboard-shortcut',
     ),
-    'a9210d03' => array(
-      'javelin-behavior',
-      'javelin-util',
-      'javelin-dom',
-      'javelin-stratcom',
-      'javelin-vector',
-    ),
     'a9f88de2' => array(
       'javelin-behavior',
       'javelin-dom',
@@ -2105,6 +2098,13 @@ return array(
       'javelin-dom',
       'phabricator-draggable-list',
     ),
+    'ecf4e799' => array(
+      'javelin-behavior',
+      'javelin-util',
+      'javelin-dom',
+      'javelin-stratcom',
+      'javelin-vector',
+    ),
     'edf8a145' => array(
       'javelin-behavior',
       'javelin-uri',
diff --git a/webroot/rsrc/js/core/behavior-fancy-datepicker.js b/webroot/rsrc/js/core/behavior-fancy-datepicker.js
index 15558dbfe1..afd5ff25ad 100644
--- a/webroot/rsrc/js/core/behavior-fancy-datepicker.js
+++ b/webroot/rsrc/js/core/behavior-fancy-datepicker.js
@@ -287,26 +287,38 @@ JX.behavior('fancy-datepicker', function(config, statics) {
   };
 
   function getValidDate() {
-    var written_date = new Date(value_y, value_m-1, value_d);
+    var year_int = parseInt(value_y, 10);
 
+    if (isNaN(year_int) || year_int < 0) {
+      return new Date();
+    }
+
+    // If the user enters "11" for the year, interpret it as "2011" (which
+    // is almost certainly what they mean) not "1911" (which is the default
+    // behavior of Javascript).
+    if (year_int < 70) {
+      year_int += 2000;
+    }
+
+    var month_int = parseInt(value_m, 10);
+    if (isNaN(month_int) || month_int < 1 || month_int > 12) {
+      return new Date();
+    }
+
+    // In Javascript, January is "0", not "1", so adjust the value down.
+    month_int = month_int - 1;
+
+    var day_int = parseInt(value_d, 10);
+    if (isNaN(day_int) || day_int < 1 || day_int > 31) {
+      return new Date();
+    }
+
+    var written_date = new Date(year_int, month_int, day_int);
     if (isNaN(written_date.getTime())) {
       return new Date();
-    } else {
-      //year 01 should be 2001, not 1901
-      if (written_date.getYear() < 70) {
-        value_y += 2000;
-        written_date = new Date(value_y, value_m-1, value_d);
-      }
-
-      // adjust for a date like February 31
-      var adjust = 1;
-      while (written_date.getMonth() !== value_m-1) {
-        written_date = new Date(value_y, value_m-1, value_d-adjust);
-        adjust++;
-      }
-
-      return written_date;
     }
+
+    return written_date;
   }