diff --git a/lib/Horde/Date.php b/lib/Horde/Date.php
index f4c62be..3e061d8 100644
--- a/lib/Horde/Date.php
+++ b/lib/Horde/Date.php
@@ -1543,7 +1543,7 @@ protected function _initializeFromArray($date)
 
     protected function _initializeFromObject($date)
     {
-        if ($date instanceof DateTime) {
+        if ($date instanceof DateTimeInterface) {
             $this->_year  = (int) $date->format('Y');
             $this->_month = (int) $date->format('m');
             $this->_mday  = (int) $date->format('d');
@@ -1551,19 +1551,25 @@ protected function _initializeFromObject($date)
             $this->_min   = (int) $date->format('i');
             $this->_sec   = (int) $date->format('s');
             $this->_initializeTimezone($date->getTimezone()->getName());
-        } else {
-            $is_horde_date = $date instanceof Horde_Date;
+
+            return;
+        }
+
+        if ($date instanceof Horde_Date) {
             foreach (['year', 'month', 'mday', 'hour', 'min', 'sec'] as $key) {
-                if ($is_horde_date || isset($date->$key)) {
-                    $this->{'_' . $key} = (int) $date->$key;
-                }
+                $this->{'_' . $key} = (int) $date->$key;
             }
-            if (!$is_horde_date) {
-                $this->_correct();
-            } else {
-                $this->_initializeTimezone($date->timezone);
+            $this->_initializeTimezone($date->timezone);
+
+            return;
+        }
+
+        foreach (['year', 'month', 'mday', 'hour', 'min', 'sec'] as $key) {
+            if (isset($date->$key)) {
+                $this->{'_' . $key} = (int) $date->$key;
             }
         }
+        $this->_correct();
     }
 
     protected function _initializeTimezone($timezone)
diff --git a/test/Unnamespaced/DateTest.php b/test/Unnamespaced/DateTest.php
index a27ff56..6534ba6 100644
--- a/test/Unnamespaced/DateTest.php
+++ b/test/Unnamespaced/DateTest.php
@@ -12,13 +12,14 @@
 use date_default_timezone_get;
 use date_default_timezone_set;
 use DateTime;
+use DateTimeImmutable;
 use DateTimeZone;
+use Horde\Date\Format;
 use Horde_Date;
 use Horde_Date_Span;
 use PHPUnit\Framework\TestCase;
 use stdClass;
 use Horde_Date_Exception;
-use Horde\Date\Format;
 
 /**
  * @category   Horde
@@ -76,6 +77,34 @@ public function testConstructor()
         $date = new Horde_Date($dt);
         $this->assertEquals('2011-12-10 03:05:06', (string) $date);
 
+        $dti = new DateTimeImmutable('2026-06-23 12:00:00', new DateTimeZone('UTC'));
+        $date = new Horde_Date($dti);
+        $this->assertEquals(2026, $date->year);
+        $this->assertEquals(6, $date->month);
+        $this->assertEquals(23, $date->mday);
+        $this->assertEquals(12, $date->hour);
+        $this->assertEquals(0, $date->min);
+        $this->assertEquals(0, $date->sec);
+        $this->assertEquals('UTC', $date->timezone);
+
+        /* DateTimeImmutable with a non-UTC timezone must preserve the zone. */
+        $dti = new DateTimeImmutable('2026-06-23 12:00:00', new DateTimeZone('America/New_York'));
+        $date = new Horde_Date($dti);
+        $this->assertEquals('2026-06-23 12:00:00', (string) $date);
+        $this->assertEquals('America/New_York', $date->timezone);
+
+        $parsed = Format::parseDateTime(
+            '23.06.2026 12:00',
+            '%d.%m.%Y',
+            'HH:mm',
+            'de_DE'
+        );
+        $date = new Horde_Date($parsed->toDateTimeImmutable());
+        $this->assertEquals(2026, $date->year);
+        $this->assertEquals(6, $date->month);
+        $this->assertEquals(23, $date->mday);
+        $this->assertGreaterThan(0, $date->timestamp());
+
         // Test creating Horde_Date from a string that will use DateTime
         // internally to parse the date.
         $date = new Horde_Date('2014-03-20 5:00PM');