diff --git a/Tests/LibCore/TestLibCoreDateTime.cpp b/Tests/LibCore/TestLibCoreDateTime.cpp
index d412ce6b1d3..29017a8482e 100644
--- a/Tests/LibCore/TestLibCoreDateTime.cpp
+++ b/Tests/LibCore/TestLibCoreDateTime.cpp
@@ -8,7 +8,7 @@
 #include <AK/String.h>
 #include <AK/StringView.h>
 #include <LibCore/DateTime.h>
-#include <LibCore/System.h>
+#include <LibCore/Environment.h>
 #include <LibTest/TestCase.h>
 #include <time.h>
 
@@ -16,8 +16,8 @@ class TimeZoneGuard {
 public:
     explicit TimeZoneGuard(StringView time_zone)
     {
-        if (auto const* current_time_zone = getenv("TZ"))
-            m_time_zone = MUST(String::from_utf8({ current_time_zone, strlen(current_time_zone) }));
+        if (auto current_time_zone = Core::Environment::get("TZ"sv); current_time_zone.has_value())
+            m_time_zone = MUST(String::from_utf8(*current_time_zone));
 
         update(time_zone);
     }
@@ -25,16 +25,16 @@ public:
     ~TimeZoneGuard()
     {
         if (m_time_zone.has_value())
-            TRY_OR_FAIL(Core::System::setenv("TZ"sv, *m_time_zone, true));
+            TRY_OR_FAIL(Core::Environment::set("TZ"sv, *m_time_zone, Core::Environment::Overwrite::Yes));
         else
-            TRY_OR_FAIL(Core::System::unsetenv("TZ"sv));
+            TRY_OR_FAIL(Core::Environment::unset("TZ"sv));
 
         tzset();
     }
 
     void update(StringView time_zone)
     {
-        TRY_OR_FAIL(Core::System::setenv("TZ"sv, time_zone, true));
+        TRY_OR_FAIL(Core::Environment::set("TZ"sv, time_zone, Core::Environment::Overwrite::Yes));
         tzset();
     }
 
diff --git a/Tests/LibJS/test-js.cpp b/Tests/LibJS/test-js.cpp
index bed738fe2d1..538b6fd4bad 100644
--- a/Tests/LibJS/test-js.cpp
+++ b/Tests/LibJS/test-js.cpp
@@ -5,7 +5,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
-#include <LibCore/System.h>
+#include <LibCore/Environment.h>
 #include <LibJS/Runtime/ArrayBuffer.h>
 #include <LibTest/JavaScriptTestRunner.h>
 #include <stdlib.h>
@@ -95,14 +95,14 @@ TESTJS_GLOBAL_FUNCTION(set_time_zone, setTimeZone)
 {
     auto current_time_zone = JS::js_null();
 
-    if (auto const* time_zone = getenv("TZ"))
-        current_time_zone = JS::PrimitiveString::create(vm, StringView { time_zone, strlen(time_zone) });
+    if (auto time_zone = Core::Environment::get("TZ"sv); time_zone.has_value())
+        current_time_zone = JS::PrimitiveString::create(vm, *time_zone);
 
     if (auto time_zone = vm.argument(0); time_zone.is_null()) {
-        if (auto result = Core::System::unsetenv("TZ"sv); result.is_error())
+        if (auto result = Core::Environment::unset("TZ"sv); result.is_error())
             return vm.throw_completion<JS::InternalError>(MUST(String::formatted("Could not unset time zone: {}", result.error())));
     } else {
-        if (auto result = Core::System::setenv("TZ"sv, TRY(time_zone.to_string(vm)), true); result.is_error())
+        if (auto result = Core::Environment::set("TZ"sv, TRY(time_zone.to_string(vm)), Core::Environment::Overwrite::Yes); result.is_error())
             return vm.throw_completion<JS::InternalError>(MUST(String::formatted("Could not set time zone: {}", result.error())));
     }