MC-36718: DOB issue: leading zero is missing for single digit day

Author: tsviklinskyi

app/code/Magento/Customer/Block/Widget/Dob.php

@@ -281,7 +281,7 @@ public function getHtmlExtraParams()
      */
     public function getDateFormat()
     {
-        $dateFormat = $this->_localeDate->getDateFormatWithLongYear();
+        $dateFormat = $this->setTwoDayPlaces($this->_localeDate->getDateFormatWithLongYear());
         /** Escape RTL characters which are present in some locales and corrupt formatting */
         $escapedDateFormat = preg_replace('/[^MmDdYy\/\.\-]/', '', $dateFormat);
 
@@ -377,4 +377,19 @@ public function getFirstDay()
             \Magento\Store\Model\ScopeInterface::SCOPE_STORE
         );
     }
+
+    /**
+     * Set 2 places for day value in format string
+     *
+     * @param string $format
+     * @return string
+     */
+    private function setTwoDayPlaces(string $format): string
+    {
+        return preg_replace(
+            '/(?<!d)d(?!d)/',
+            'dd',
+            $format
+        );
+    }
 }

app/code/Magento/Customer/Test/Unit/Block/Widget/DobTest.php

@@ -51,7 +51,7 @@ class DobTest extends TestCase
     const YEAR = '2014';
 
     // Value of date('Y', strtotime(self::DATE))
-    const DATE_FORMAT = 'M/d/y';
+    const DATE_FORMAT = 'M/dd/y';
 
     /** Constants used by Dob::setDateInput($code, $html) */
     const DAY_HTML =
@@ -356,11 +356,15 @@ public function getDateFormatDataProvider(): array
             [
                 'ar_SA',
                 preg_replace(
-                    '/[^MmDdYy\/\.\-]/',
-                    '',
-                    (new DateFormatterFactory())
-                        ->create('ar_SA', \IntlDateFormatter::SHORT, \IntlDateFormatter::NONE)
-                        ->getPattern()
+                    '/(?<!d)d(?!d)/',
+                    'dd',
+                    preg_replace(
+                        '/[^MmDdYy\/\.\-]/',
+                        '',
+                        (new DateFormatterFactory())
+                            ->create('ar_SA', \IntlDateFormatter::SHORT, \IntlDateFormatter::NONE)
+                            ->getPattern()
+                    )
                 )
             ],
             [Resolver::DEFAULT_LOCALE, self::DATE_FORMAT],