diff --git a/tests/ClockMockTest.php b/tests/ClockMockTest.php
index 2a68cd2..ee777dc 100644
--- a/tests/ClockMockTest.php
+++ b/tests/ClockMockTest.php
@@ -184,14 +184,45 @@ public function test_gmstrftime()
 
     public function dateProvider_gmmktime(): array
     {
+        // NOTE: for all datasets, hour in freezeDateTime is completely irrelevant because always overridden by $hour
+        // parameter provided to gmmktime. Also, in expectedDateTime hour is always "13" because hour 10 in GMT
+        // corresponds to hour 13 when we are in +03:00 offset.
         return [
-            ['2022-04-04 14:26:29.123456', [10], '2022-04-04 13:26:29.123456'],
-            ['2022-04-04 14:26:29.123456', [10, 10], '2022-04-04 13:10:29.123456'],
-            ['2022-04-04 14:26:29.123456', [10, null, 10], '2022-04-04 13:26:10.123456'],
-            ['2022-04-04 14:26:29.123456', [10, null, null, 10], '2022-10-04 13:26:29.123456'],
-            ['2022-04-04 14:26:29.123456', [10, null, null, null, 10], '2022-04-10 13:26:29.123456'],
-            ['2022-04-04 14:26:29.123456', [10, null, null, null, null, 10], '2010-04-04 13:26:29.123456'],
-            ['2022-04-04 14:26:29.123456', [10, 10, 10, 10, 10, 10], '2010-10-10 13:10:10.123456'],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10],
+                '2022-04-04T13:26:29+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, 10],
+                '2022-04-04T13:10:29+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, null, 10],
+                '2022-04-04T13:26:10+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, null, null, 10],
+                '2022-10-04T13:26:29+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, null, null, null, 10],
+                '2022-04-10T13:26:29+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, null, null, null, null, 10],
+                '2010-04-04T13:26:29+00:00'
+            ],
+            [
+                '2022-04-04T05:26:29+03:00',
+                [10, 10, 10, 10, 10, 10],
+                '2010-10-10T13:10:10+00:00'
+            ],
         ];
     }
 
@@ -200,9 +231,9 @@ public function dateProvider_gmmktime(): array
      */
     public function test_gmmktime(string $freezeDateTime, array $mktimeArgs, string $expectedDateTime)
     {
-        ClockMock::freeze((new \DateTime($freezeDateTime))->setTimezone(new \DateTimeZone('Europe/Kiev')));
+        ClockMock::freeze(new \DateTime($freezeDateTime));
 
-        $this->assertEquals($expected = strtotime($expectedDateTime), $actual = gmmktime(...$mktimeArgs));
+        $this->assertEquals($expectedDateTime, date(DATE_ATOM, gmmktime(...$mktimeArgs)));
     }
 
     public function test_idate()