diff --git a/tests/system/I18n/TimeLegacyTest.php b/tests/system/I18n/TimeLegacyTest.php
index 36907988349d..9f013a0ddcbe 100644
--- a/tests/system/I18n/TimeLegacyTest.php
+++ b/tests/system/I18n/TimeLegacyTest.php
@@ -399,10 +399,15 @@ public function testGetTimestamp(): void
 
     public function testGetAge(): void
     {
+        // setTestNow() does not work to parse().
         $time = TimeLegacy::parse('5 years ago');
 
-        $this->assertSame(5, $time->getAge());
-        $this->assertSame(5, $time->age);
+        // Considers leap year
+        $now      = TimeLegacy::now();
+        $expected = ($now->day === '29' && $now->month === '2') ? 4 : 5;
+
+        $this->assertSame($expected, $time->getAge());
+        $this->assertSame($expected, $time->age);
     }
 
     public function testAgeNow(): void
diff --git a/tests/system/I18n/TimeTest.php b/tests/system/I18n/TimeTest.php
index d60fb4410a03..f5bca98268fb 100644
--- a/tests/system/I18n/TimeTest.php
+++ b/tests/system/I18n/TimeTest.php
@@ -406,10 +406,15 @@ public function testGetTimestamp(): void
      */
     public function testGetAge(): void
     {
+        // setTestNow() does not work to parse().
         $time = Time::parse('5 years ago');
 
-        $this->assertSame(5, $time->getAge());
-        $this->assertSame(5, $time->age);
+        // Considers leap year
+        $now      = Time::now();
+        $expected = ($now->day === '29' && $now->month === '2') ? 4 : 5;
+
+        $this->assertSame($expected, $time->getAge());
+        $this->assertSame($expected, $time->age);
     }
 
     public function testAgeNow(): void