diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index ec3a74d..fba17bb 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-versions: ['8.2', '8.3']
+        php-versions: ['8.3', '8.4']
         dependency-versions: ['lowest', 'highest']
     runs-on: ubuntu-latest
     steps:
diff --git a/composer.json b/composer.json
index 5e4129b..38189bd 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,7 @@
     },
     "require": {
         "ext-intl": "*",
-        "php": "^7.4|^8.0",
+        "php": "^8.3",
         "symfony/framework-bundle": "^6.0|^7.0",
         "assoconnect/php-date": "^2.11",
         "doctrine/dbal": "^2.10|^3.0",
diff --git a/src/AbsoluteDateClock.php b/src/AbsoluteDateClock.php
index a129c15..ba45494 100644
--- a/src/AbsoluteDateClock.php
+++ b/src/AbsoluteDateClock.php
@@ -17,7 +17,7 @@ public static function now(\DateTimeZone $timeZone): AbsoluteDate
     /**
      * @throws \DateMalformedStringException
      */
-    public static function relative(string $relative = 'now', \DateTimeZone $timezone = null): AbsoluteDate
+    public static function relative(string $relative = 'now', ?\DateTimeZone $timezone = null): AbsoluteDate
     {
         return AbsoluteDate::createInTimezone($timezone ?? new \DateTimeZone('UTC'), new DatePoint($relative));
     }
diff --git a/src/Normalizer/AbsoluteDateNormalizer.php b/src/Normalizer/AbsoluteDateNormalizer.php
index 4774219..034cd2d 100644
--- a/src/Normalizer/AbsoluteDateNormalizer.php
+++ b/src/Normalizer/AbsoluteDateNormalizer.php
@@ -24,7 +24,7 @@ class AbsoluteDateNormalizer implements NormalizerInterface, DenormalizerInterfa
      * @param mixed[] $context
      * @throws InvalidArgumentException
      */
-    public function normalize($object, string $format = null, array $context = []): string
+    public function normalize($object, ?string $format = null, array $context = []): string
     {
         if (!$object instanceof AbsoluteDate) {
             throw new InvalidArgumentException(sprintf(
@@ -42,7 +42,7 @@ public function normalize($object, string $format = null, array $context = []):
      * {@inheritdoc}
      * @param mixed[] $context
      */
-    public function supportsNormalization(mixed $data, string $format = null, array $context = []): bool
+    public function supportsNormalization(mixed $data, ?string $format = null, array $context = []): bool
     {
         return $data instanceof AbsoluteDate;
     }
@@ -53,7 +53,7 @@ public function supportsNormalization(mixed $data, string $format = null, array
      * @param mixed[] $context
      * @throws NotNormalizableValueException
      */
-    public function denormalize($data, string $type, string $format = null, array $context = []): ?AbsoluteDate
+    public function denormalize($data, string $type, ?string $format = null, array $context = []): ?AbsoluteDate
     {
         $dateTimeFormat = $context[self::FORMAT_KEY] ?? AbsoluteDate::DEFAULT_DATE_FORMAT;
 
diff --git a/src/Translatable/AbsoluteDateTranslatable.php b/src/Translatable/AbsoluteDateTranslatable.php
index f5cc045..21407d7 100644
--- a/src/Translatable/AbsoluteDateTranslatable.php
+++ b/src/Translatable/AbsoluteDateTranslatable.php
@@ -34,7 +34,7 @@ public function __construct(
         $this->timezone = new DateTimeZone('UTC');
     }
 
-    public function trans(TranslatorInterface $translator, string $locale = null): string
+    public function trans(TranslatorInterface $translator, ?string $locale = null): string
     {
         if (null === $locale) {
             $locale = $translator->getLocale();
diff --git a/src/Twig/Extension/AbsoluteDateExtension.php b/src/Twig/Extension/AbsoluteDateExtension.php
index 17b5650..fcd6120 100644
--- a/src/Twig/Extension/AbsoluteDateExtension.php
+++ b/src/Twig/Extension/AbsoluteDateExtension.php
@@ -26,7 +26,7 @@ public function getFilters(): array
         ];
     }
 
-    public function formatAbsoluteDate(AbsoluteDate $date, string $locale = null): string
+    public function formatAbsoluteDate(AbsoluteDate $date, ?string $locale = null): string
     {
         return (new AbsoluteDateTranslatable($date))->trans($this->translator, $locale);
     }