diff --git a/date.field.inc b/date.field.inc
index 7acd7ef..e1777b7 100644
--- a/date.field.inc
+++ b/date.field.inc
@@ -189,7 +189,7 @@ function date_field_info() {
     'instance_settings' => array(
       'default_value' => 'now',
       'default_value_code' => '',
-      'default_value2' => 'blank',
+      'default_value2' => 'same',
       'default_value_code2' => '',
     ),
     // Integrate with the Entity Metadata module.
diff --git a/date.js b/date.js
new file mode 100644
index 0000000..2e60175
--- /dev/null
+++ b/date.js
@@ -0,0 +1,159 @@
+(function ($) {
+
+
+Drupal.behaviors.dateSelect = {};
+
+Drupal.behaviors.dateSelect.attach = function (context, settings) {
+  var $widget = $('.form-type-date-select').parents('fieldset').once('date');
+  var i;
+  for (i = 0; i < $widget.length; i++) {
+    new Drupal.date.EndDateHandler($widget[i]);
+  }
+};
+
+Drupal.date = Drupal.date || {};
+
+/**
+ * Constructor for the EndDateHandler object.
+ *
+ * The EndDateHandler is responsible for synchronizing a date select widget's
+ * end date with its start date. This behavior lasts until the user
+ * interacts with the end date widget.
+ *
+ * @param widget
+ *   The fieldset DOM element containing the from and to dates.
+ */
+Drupal.date.EndDateHandler = function (widget) {
+  this.$widget = $(widget);
+  this.$start = this.$widget.find('.form-type-date-select[class$=value]');
+  this.$end = this.$widget.find('.form-type-date-select[class$=value2]');
+  if (this.$end.length == 0) {
+    return;
+  }
+  this.initializeSelects();
+  // Only act on date fields where the end date is completely blank or already
+  // the same as the start date. Otherwise, we do not want to override whatever
+  // the default value was.
+  if (this.endDateIsBlank() || this.endDateIsSame()) {
+    this.bindClickHandlers();
+    // Start out with identical start and end dates.
+    this.syncEndDate();
+  }
+};
+
+/**
+ * Store all the select dropdowns in an array on the object, for later use.
+ */
+Drupal.date.EndDateHandler.prototype.initializeSelects = function () {
+  var $starts = this.$start.find('select');
+  var $end, $start, endId, i, id;
+  this.selects = {};
+  for (i = 0; i < $starts.length; i++) {
+    $start = $($starts[i]);
+    id = $start.attr('id');
+    endId = id.replace('-value-', '-value2-');
+    $end = $('#' + endId);
+    this.selects[id] = {
+      'id': id,
+      'start': $start,
+      'end': $end
+    };
+  }
+};
+
+/**
+ * Returns true if all dropdowns in the end date widget are blank.
+ */
+Drupal.date.EndDateHandler.prototype.endDateIsBlank = function () {
+  var id;
+  for (id in this.selects) {
+    if (this.selects.hasOwnProperty(id)) {
+      if (this.selects[id].end.val() != '') {
+        return false;
+      }
+    }
+  }
+  return true;
+};
+
+/**
+ * Returns true if the end date widget has the same value as the start date.
+ */
+Drupal.date.EndDateHandler.prototype.endDateIsSame = function () {
+  var id;
+  for (id in this.selects) {
+    if (this.selects.hasOwnProperty(id)) {
+      if (this.selects[id].end.val() != this.selects[id].start.val()) {
+        return false;
+      }
+    }
+  }
+  return true;
+};
+
+/**
+ * Add a click handler to each of the start date's select dropdowns.
+ */
+Drupal.date.EndDateHandler.prototype.bindClickHandlers = function () {
+  var id;
+  for (id in this.selects) {
+    if (this.selects.hasOwnProperty(id)) {
+      this.selects[id].start.bind('click.endDateHandler', this.startClickHandler.bind(this));
+      this.selects[id].end.bind('focus', this.endFocusHandler.bind(this));
+    }
+  }
+};
+
+/**
+ * Click event handler for each of the start date's select dropdowns.
+ */
+Drupal.date.EndDateHandler.prototype.startClickHandler = function (event) {
+  this.syncEndDate();
+};
+
+/**
+ * Focus event handler for each of the end date's select dropdowns.
+ */
+Drupal.date.EndDateHandler.prototype.endFocusHandler = function (event) {
+  var id;
+  for (id in this.selects) {
+    if (this.selects.hasOwnProperty(id)) {
+      this.selects[id].start.unbind('click.endDateHandler');
+    }
+  }
+  $(event.target).unbind('focus', this.endFocusHandler);
+};
+
+Drupal.date.EndDateHandler.prototype.syncEndDate = function () {
+  var id;
+  for (id in this.selects) {
+    if (this.selects.hasOwnProperty(id)) {
+      this.selects[id].end.val(this.selects[id].start.val());
+    }
+  }
+};
+
+}(jQuery));
+
+/**
+ * Function.prototype.bind polyfill for older browsers.
+ * https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/bind
+ */
+if (!Function.prototype.bind) {
+  Function.prototype.bind = function (oThis) {
+    if (typeof this !== "function") // closest thing possible to the ECMAScript 5 internal IsCallable function
+      throw new TypeError("Function.prototype.bind - what is trying to be fBound is not callable");
+
+    var aArgs = Array.prototype.slice.call(arguments, 1),
+        fToBind = this,
+        fNOP = function () {},
+        fBound = function () {
+          return fToBind.apply(this instanceof fNOP ? this : oThis || window, aArgs.concat(Array.prototype.slice.call(arguments)));
+        };
+
+    fNOP.prototype = this.prototype;
+    fBound.prototype = new fNOP();
+
+    return fBound;
+  };
+}
diff --git a/date_elements.inc b/date_elements.inc
index 3e702cd..aa30e02 100644
--- a/date_elements.inc
+++ b/date_elements.inc
@@ -321,6 +321,7 @@ function date_combo_element_process($element, &$form_state, $form) {
     case 'date_select':
       $element[$from_field]['#type'] = 'date_select';
       $element[$from_field]['#theme_wrappers'] = array('date_select');
+      $element['#attached']['js'][] = drupal_get_path('module', 'date') . '/date.js';
       break;
     case 'date_popup':
       $element[$from_field]['#type'] = 'date_popup';
@@ -344,7 +345,9 @@ function date_combo_element_process($element, &$form_state, $form) {
     $element[$to_field]['#required'] = FALSE;
     $element[$to_field]['#weight'] += .2;
     $element[$to_field]['#prefix'] = '';
-    $description .= ' ' . t("Empty 'End date' values will use the 'Start date' values.");
+    // Users with JS enabled will never see initially blank values for the end
+    // date (see Drupal.date.EndDateHandler()), so hide the message for them.
+    $description .= '<span class="js-hide"> ' . t("Empty 'End date' values will use the 'Start date' values.") . '</span>';
     $element['#fieldset_description'] = $description;
     if ($field['settings']['todate'] == 'optional') {
       $element[$to_field]['#states'] = array(