diff --git a/src/Utilities/Date.php b/src/Utilities/Date.php
index 421b411..e8d870d 100644
--- a/src/Utilities/Date.php
+++ b/src/Utilities/Date.php
@@ -235,20 +235,20 @@ class Date
      *
      * @return int
      */
-    public static function getCurrentDayOfWeek()
+    public static function getCurrentDayOfWeek(): int
     {
         $now = new DateTime();
 
-        $year = $now->format('Y');
-        $month = $now->format('m');
-        $day = $now->format('d');
+        $year = (int)$now->format('Y');
+        $month = (int)$now->format('m');
+        $day = (int)$now->format('d');
 
         return self::getDayOfWeek($year, $month, $day);
     }
 
     /**
      * Returns day of week (number 0 to 6, 0 - sunday, 6 - saturday).
-     * Based on the Zeller's algorithm (http://pl.wikipedia.org/wiki/Kalendarz_wieczny).
+     * Based on the Zeller's algorithm (https://en.wikipedia.org/wiki/Perpetual_calendar).
      *
      * @param int $year  The year value
      * @param int $month The month value
@@ -257,12 +257,8 @@ class Date
      * @throws UnknownDatePartTypeException
      * @return int
      */
-    public static function getDayOfWeek($year, $month, $day)
+    public static function getDayOfWeek(int $year, int $month, int $day): int
     {
-        $year = (int)$year;
-        $month = (int)$month;
-        $day = (int)$day;
-
         // Oops, given year is incorrect
         if ($year <= 0) {
             throw UnknownDatePartTypeException::createException(DatePartType::YEAR, $year);
@@ -299,13 +295,13 @@ class Date
      *
      * @return string
      */
-    public static function getCurrentDayOfWeekName()
+    public static function getCurrentDayOfWeekName(): string
     {
         $now = new DateTime();
 
-        $year = $now->format('Y');
-        $month = $now->format('m');
-        $day = $now->format('d');
+        $year = (int)$now->format('Y');
+        $month = (int)$now->format('m');
+        $day = (int)$now->format('d');
 
         return self::getDayOfWeekName($year, $month, $day);
     }
diff --git a/tests/Utilities/DateTest.php b/tests/Utilities/DateTest.php
index a899f48..a827eb0 100644
--- a/tests/Utilities/DateTest.php
+++ b/tests/Utilities/DateTest.php
@@ -228,7 +228,7 @@ class DateTest extends BaseTestCase
      *
      * @dataProvider provideIncorrectYearMonthDay
      */
-    public function testGetDayOfWeekIncorrectValues($year, $month, $day): void
+    public function testGetDayOfWeekIncorrectValues(int $year, int $month, int $day): void
     {
         $this->expectException(UnknownDatePartTypeException::class);
         self::assertEmpty(Date::getDayOfWeek($year, $month, $day));
@@ -241,7 +241,7 @@ class DateTest extends BaseTestCase
      *
      * @dataProvider provideYearMonthDay
      */
-    public function testGetDayOfWeek($year, $month, $day): void
+    public function testGetDayOfWeek(int $year, int $month, int $day): void
     {
         self::assertRegExp('/^[0-6]{1}$/', (string)Date::getDayOfWeek($year, $month, $day));
     }
@@ -766,20 +766,8 @@ class DateTest extends BaseTestCase
      *
      * @return Generator
      */
-    public function provideIncorrectYearMonthDay()
+    public function provideIncorrectYearMonthDay(): Generator
     {
-        yield[
-            null,
-            null,
-            null,
-        ];
-
-        yield[
-            '',
-            '',
-            '',
-        ];
-
         yield[
             0,
             0,