diff --git a/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php b/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
index 1e57c91004d8..8d329f106293 100644
--- a/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
+++ b/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php
@@ -761,7 +761,9 @@ public function setAttribute($key, $value)
         // If an attribute is listed as a "date", we'll convert it from a DateTime
         // instance into a form proper for storage on the database tables using
         // the connection grammar's date format. We will auto set the values.
-        elseif ($value && $this->isDateAttribute($key)) {
+        elseif ($value && $this->isDateAttribute($key) && !(
+            $this->hasCast($key, ['custom_datetime', 'immutable_custom_datetime']) && is_string($value)
+        )) {
             $value = $this->fromDateTime($value);
         }
 
@@ -1643,7 +1645,7 @@ public function originalIsEquivalent($key)
             return true;
         } elseif (is_null($attribute)) {
             return false;
-        } elseif ($this->isDateAttribute($key) || $this->isDateCastable($key)) {
+        } elseif ($this->isDateAttribute($key)) {
             return $this->fromDateTime($attribute) ===
                 $this->fromDateTime($original);
         } elseif ($this->hasCast($key, ['object', 'collection'])) {
diff --git a/tests/Integration/Database/EloquentModelDateCastingTest.php b/tests/Integration/Database/EloquentModelDateCastingTest.php
index 474c5a6e508a..e023bcefc0a3 100644
--- a/tests/Integration/Database/EloquentModelDateCastingTest.php
+++ b/tests/Integration/Database/EloquentModelDateCastingTest.php
@@ -40,7 +40,46 @@ public function testDatesAreCustomCastable()
         $this->assertInstanceOf(Carbon::class, $user->datetime_field);
     }
 
-    public function testCustomDateCastsAreComparedAsDates()
+    public function testDatesFormattedAttributeBindings()
+    {
+        $bindings = [];
+
+        $this->app->make('db')->listen(static function ($query) use (&$bindings) {
+            $bindings = $query->bindings;
+        });
+
+        $user = TestModel1::create([
+            'date_field' => '2019-10',
+            'datetime_field' => new CarbonImmutable('2019-10-01 10:15:20'),
+            'immutable_date_field' => new CarbonImmutable('2019-10-01'),
+            'immutable_datetime_field' => '2019-10-01 10:15',
+        ]);
+
+        $this->assertSame(['2019-10', '2019-10-01 10:15:20', '2019-10-01 00:00:00', '2019-10-01 10:15'], $bindings);
+    }
+
+    public function testCustomDateCastsAreComparedAsDatesForStringValues()
+    {
+        /** @var TestModel1 */
+        $user = TestModel1::create([
+            'date_field' => '2019-10-01',
+            'datetime_field' => '2019-10-01 10:15:20',
+            'immutable_date_field' => '2019-10-01',
+            'immutable_datetime_field' => '2019-10-01 10:15:20',
+        ]);
+
+        $user->date_field = '2019-10-01';
+        $user->datetime_field = '2019-10-01 10:15:20';
+        $user->immutable_date_field = '2019-10-01';
+        $user->immutable_datetime_field = '2019-10-01 10:15:20';
+
+        $this->assertArrayNotHasKey('date_field', $user->getDirty());
+        $this->assertArrayNotHasKey('datetime_field', $user->getDirty());
+        $this->assertArrayNotHasKey('immutable_date_field', $user->getDirty());
+        $this->assertArrayNotHasKey('immutable_datetime_field', $user->getDirty());
+    }
+
+    public function testCustomDateCastsAreComparedAsDatesForCarbonValues()
     {
         /** @var TestModel1 */
         $user = TestModel1::create([