diff --git a/.github/workflows/benchmarks.yml b/.github/workflows/benchmarks.yml
index 88cef877..88e4b370 100644
--- a/.github/workflows/benchmarks.yml
+++ b/.github/workflows/benchmarks.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         php-version:
-          - "8.3"
+          - "8.4"
         operating-system:
           - "ubuntu-latest"
 
diff --git a/.github/workflows/code-coverage.yml b/.github/workflows/code-coverage.yml
index c0484ea7..7fc2feef 100644
--- a/.github/workflows/code-coverage.yml
+++ b/.github/workflows/code-coverage.yml
@@ -17,7 +17,7 @@ jobs:
       - name: "installing PHP"
         uses: "shivammathur/setup-php@v2"
         with:
-          php-version: "8.3"
+          php-version: "8.4"
           ini-values: memory_limit=-1
           tools: composer:v2, cs2pr
           extensions: bcmath, mbstring, intl, sodium, json
diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
index 835c9bbf..d9376481 100644
--- a/.github/workflows/coding-standards.yml
+++ b/.github/workflows/coding-standards.yml
@@ -15,7 +15,7 @@ jobs:
       - name: "installing PHP"
         uses: "shivammathur/setup-php@v2"
         with:
-          php-version: "8.3"
+          php-version: "8.4"
           ini-values: memory_limit=-1
           tools: composer:v2, cs2pr
           extensions: bcmath, mbstring, intl, sodium, json
diff --git a/.github/workflows/documentation-check.yml b/.github/workflows/documentation-check.yml
index d583dbc2..6fb7da39 100644
--- a/.github/workflows/documentation-check.yml
+++ b/.github/workflows/documentation-check.yml
@@ -15,7 +15,7 @@ jobs:
       - name: "installing PHP"
         uses: "shivammathur/setup-php@v2"
         with:
-          php-version: "8.3"
+          php-version: "8.4"
           ini-values: memory_limit=-1
           tools: composer:v2, cs2pr
           extensions: bcmath, mbstring, intl, sodium, json
diff --git a/.github/workflows/mutation-tests.yml b/.github/workflows/mutation-tests.yml
index 7d7d0f8b..9c96e3a2 100644
--- a/.github/workflows/mutation-tests.yml
+++ b/.github/workflows/mutation-tests.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       matrix:
         php-version:
-          - "8.3"
+          - "8.4"
         operating-system:
           - "ubuntu-latest"
 
diff --git a/.github/workflows/preload-check.yml b/.github/workflows/preload-check.yml
index bf3c6e06..8cea21ac 100644
--- a/.github/workflows/preload-check.yml
+++ b/.github/workflows/preload-check.yml
@@ -15,7 +15,7 @@ jobs:
       - name: "installing PHP"
         uses: "shivammathur/setup-php@v2"
         with:
-          php-version: "8.3"
+          php-version: "8.4"
           ini-values: memory_limit=-1
           tools: composer:v2, cs2pr
           extensions: bcmath, mbstring, intl, sodium, json
diff --git a/.github/workflows/unit-tests.yml b/.github/workflows/unit-tests.yml
index cfdb3430..07a005a2 100644
--- a/.github/workflows/unit-tests.yml
+++ b/.github/workflows/unit-tests.yml
@@ -15,6 +15,7 @@ jobs:
         php-version:
           - "8.2"
           - "8.3"
+          - "8.4"
         operating-system:
           - "macos-latest"
           - "ubuntu-latest"
diff --git a/Makefile b/Makefile
index d619b7a4..8e0e50f7 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ help:
 	@awk 'BEGIN {FS = ":.*?## "} /^[a-zA-Z_\-\.]+:.*?## / {printf "\033[36m%-30s\033[0m %s\n", $$1, $$2}' $(MAKEFILE_LIST)
 
 install:                                                              			## install all dependencies for a development environment
-	composer install
+	COMPOSER_IGNORE_PLATFORM_REQ=php+ composer install
 
 coding-standard-fix:                                                            ## apply automated coding standard fixes
 	PHP_CS_FIXER_IGNORE_ENV=1 ./vendor/bin/php-cs-fixer fix --config=config/.php_cs.dist.php
diff --git a/composer.json b/composer.json
index 6127ff32..392ca0d7 100644
--- a/composer.json
+++ b/composer.json
@@ -10,7 +10,7 @@
         }
     ],
     "require": {
-        "php": "~8.2.0 || ~8.3.0",
+        "php": "~8.2.0 || ~8.3.0 || ~8.4.0",
         "ext-bcmath": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
diff --git a/composer.lock b/composer.lock
index a41893b1..a3d30aef 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "97465cc59bebf30479efdae3608e548a",
+    "content-hash": "96e8a3659280b296c7389255024734c4",
     "packages": [
         {
             "name": "revolt/event-loop",
@@ -7403,17 +7403,17 @@
     ],
     "aliases": [],
     "minimum-stability": "stable",
-    "stability-flags": [],
+    "stability-flags": {},
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "~8.2.0 || ~8.3.0",
+        "php": "~8.2.0 || ~8.3.0 || ~8.4.0",
         "ext-bcmath": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
         "ext-sodium": "*",
         "ext-intl": "*"
     },
-    "platform-dev": [],
+    "platform-dev": {},
     "plugin-api-version": "2.6.0"
 }
diff --git a/src/Psl/DateTime/DateTime.php b/src/Psl/DateTime/DateTime.php
index c1bafde1..87398c91 100644
--- a/src/Psl/DateTime/DateTime.php
+++ b/src/Psl/DateTime/DateTime.php
@@ -172,14 +172,7 @@ public static function fromParts(Timezone $timezone, int $year, Month|int $month
             $month = $month->value;
         }
 
-        /**
-         * @var IntlCalendar $calendar
-         */
-        $calendar = IntlCalendar::createInstance(
-            Internal\to_intl_timezone($timezone),
-        );
-
-        $calendar->set($year, $month - 1, $day, $hours, $minutes, $seconds);
+        $calendar = Internal\create_intl_calendar_from_date_time($timezone, $year, $month, $day, $hours, $minutes, $seconds);
 
         if ($seconds !== $calendar->get(IntlCalendar::FIELD_SECOND)) {
             throw Exception\UnexpectedValueException::forSeconds($seconds, $calendar->get(IntlCalendar::FIELD_SECOND));
diff --git a/src/Psl/DateTime/Internal/create_intl_calendar_from_date_time.php b/src/Psl/DateTime/Internal/create_intl_calendar_from_date_time.php
new file mode 100644
index 00000000..f09a21e0
--- /dev/null
+++ b/src/Psl/DateTime/Internal/create_intl_calendar_from_date_time.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Psl\DateTime\Internal;
+
+use IntlCalendar;
+use Psl\DateTime\Timezone;
+
+/**
+ * @internal
+ *
+ * @psalm-mutation-free
+ *
+ * @psalm-suppress ImpureMethodCall - `IntlCalender::setDateTime()` is mutation free, as it performs a read-only operation.
+ *
+ * @infection-ignore-all
+ */
+function create_intl_calendar_from_date_time(
+    Timezone $timezone,
+    int $year,
+    int $month,
+    int $day,
+    int $hours,
+    int $minutes,
+    int $seconds
+): IntlCalendar {
+    /**
+     * @var IntlCalendar $calendar
+     */
+    $calendar = IntlCalendar::createInstance(
+        to_intl_timezone($timezone),
+    );
+
+    if (PHP_VERSION_ID >= 80300) {
+        $calendar->setDateTime($year, $month - 1, $day, $hours, $minutes, $seconds);
+    } else {
+        // @codeCoverageIgnoreStart
+        $calendar->set($year, $month - 1, $day, $hours, $minutes, $seconds);
+        // @codeCoverageIgnoreEnd
+    }
+
+    return $calendar;
+}
diff --git a/src/Psl/Internal/Loader.php b/src/Psl/Internal/Loader.php
index 51bd3d8a..e843124b 100644
--- a/src/Psl/Internal/Loader.php
+++ b/src/Psl/Internal/Loader.php
@@ -554,6 +554,7 @@ final class Loader
         'Psl\\DateTime\\Internal\\default_timezone' => 'Psl/DateTime/Internal/default_timezone.php',
         'Psl\\DateTime\\Internal\\system_time' => 'Psl/DateTime/Internal/system_time.php',
         'Psl\\DateTime\\Internal\\high_resolution_time' => 'Psl/DateTime/Internal/high_resolution_time.php',
+        'Psl\\DateTime\\Internal\\create_intl_calendar_from_date_time' => 'Psl/DateTime/Internal/create_intl_calendar_from_date_time.php',
         'Psl\\DateTime\\Internal\\create_intl_date_formatter' => 'Psl/DateTime/Internal/create_intl_date_formatter.php',
         'Psl\\DateTime\\Internal\\parse' => 'Psl/DateTime/Internal/parse.php',
         'Psl\\DateTime\\Internal\\format_rfc3339' => 'Psl/DateTime/Internal/format_rfc3339.php',