diff --git a/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
index d3cb15e..19d57c9 100644
--- a/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -268,10 +268,11 @@ public function __construct($time = 'now', $timezone = NULL, $settings = []) {
     $prepared_timezone = $this->prepareTimezone($timezone);
 
     try {
+      $this->errors = [];
       if (!empty($prepared_time)) {
         $test = date_parse($prepared_time);
         if (!empty($test['errors'])) {
-          $this->errors[] = $test['errors'];
+          $this->errors = array_merge($this->errors, array_values($test['errors']));
         }
       }
 
@@ -285,7 +286,6 @@ public function __construct($time = 'now', $timezone = NULL, $settings = []) {
 
     // Clean up the error messages.
     $this->checkErrors();
-    $this->errors = array_unique($this->errors);
   }
 
   /**
@@ -442,7 +442,7 @@ protected function prepareFormat($format) {
   public function checkErrors() {
     $errors = \DateTime::getLastErrors();
     if (!empty($errors['errors'])) {
-      $this->errors += $errors['errors'];
+      $this->errors = array_merge($this->errors, array_values($errors['errors']));
     }
     // Most warnings are messages that the date could not be parsed
     // which causes it to be altered. For validation purposes, a warning
@@ -451,6 +451,8 @@ public function checkErrors() {
     if (!empty($errors['warnings'])) {
       $this->errors[] = 'The date is invalid.';
     }
+
+    $this->errors = array_values(array_unique($this->errors));
   }
 
   /**
diff --git a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
index 95fdd64..9b47bd0 100644
--- a/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
+++ b/core/tests/Drupal/Tests/Component/Datetime/DateTimePlusTest.php
@@ -670,4 +670,96 @@ public function providerTestInvalidDateDiff() {
     ];
   }
 
+  /**
+   * Tests invalid values passed to constructor.
+   *
+   * @param string $time
+   *   A date/time string.
+   * @param string[] $errors
+   *   A array of errors messages.
+   *
+   * @covers ::__construct
+   *
+   * @dataProvider providerTestInvalidConstructor
+   */
+  public function testInvalidConstructor($time, array $errors) {
+    $date = new DateTimePlus($time);
+
+    // Make sure the parsed date/time has errors.
+    $this->assertEquals(TRUE, $date->hasErrors());
+
+    // Make sure all of the errors are unique strings.
+    $this->assertEquals($errors, $date->getErrors());
+  }
+
+  /**
+   * Provider for testInvalidConstructor().
+   *
+   * @return array
+   *   An array of invalid date/time strings, and corresponding error messages.
+   */
+  public function providerTestInvalidConstructor() {
+    return [
+      [
+        'YYYY-MM-DD',
+        [
+          'The timezone could not be found in the database',
+          'Unexpected character',
+          'Double timezone specification',
+        ],
+      ],
+      [
+        '2017-MM-DD',
+        [
+          'Unexpected character',
+          'The timezone could not be found in the database',
+        ],
+      ],
+      [
+        'YYYY-03-DD',
+        [
+          'The timezone could not be found in the database',
+          'Unexpected character',
+          'Double timezone specification',
+        ],
+      ],
+      [
+        'YYYY-MM-07',
+        [
+          'The timezone could not be found in the database',
+          'Unexpected character',
+          'Double timezone specification',
+        ],
+      ],
+      [
+        '2017-13-55',
+        [
+          'Unexpected character',
+        ],
+      ],
+      [
+        'YYYY-MM-DD hh:mm:ss',
+        [
+          'The timezone could not be found in the database',
+          'Unexpected character',
+          'Double timezone specification',
+        ],
+      ],
+      [
+        '2017-03-07 25:70:80',
+        [
+          'Unexpected character',
+          'Double time specification',
+        ],
+      ],
+      [
+        'lorem ipsum dolor sit amet',
+        [
+          'The timezone could not be found in the database',
+          'Double timezone specification',
+        ],
+      ],
+    ];
+  }
+
 }