diff --git a/Tests/LibCore/TestLibCoreDateTime.cpp b/Tests/LibCore/TestLibCoreDateTime.cpp
index 29017a8482e..22bd928cfc5 100644
--- a/Tests/LibCore/TestLibCoreDateTime.cpp
+++ b/Tests/LibCore/TestLibCoreDateTime.cpp
@@ -10,6 +10,7 @@
 #include <LibCore/DateTime.h>
 #include <LibCore/Environment.h>
 #include <LibTest/TestCase.h>
+#include <LibUnicode/TimeZone.h>
 #include <time.h>
 
 class TimeZoneGuard {
@@ -29,12 +30,14 @@ public:
         else
             TRY_OR_FAIL(Core::Environment::unset("TZ"sv));
 
+        Unicode::clear_system_time_zone_cache();
         tzset();
     }
 
     void update(StringView time_zone)
     {
         TRY_OR_FAIL(Core::Environment::set("TZ"sv, time_zone, Core::Environment::Overwrite::Yes));
+        Unicode::clear_system_time_zone_cache();
         tzset();
     }
 
diff --git a/Tests/LibJS/test-js.cpp b/Tests/LibJS/test-js.cpp
index 538b6fd4bad..9b2d15e4fa3 100644
--- a/Tests/LibJS/test-js.cpp
+++ b/Tests/LibJS/test-js.cpp
@@ -8,6 +8,7 @@
 #include <LibCore/Environment.h>
 #include <LibJS/Runtime/ArrayBuffer.h>
 #include <LibTest/JavaScriptTestRunner.h>
+#include <LibUnicode/TimeZone.h>
 #include <stdlib.h>
 #include <time.h>
 
@@ -106,6 +107,7 @@ TESTJS_GLOBAL_FUNCTION(set_time_zone, setTimeZone)
             return vm.throw_completion<JS::InternalError>(MUST(String::formatted("Could not set time zone: {}", result.error())));
     }
 
+    Unicode::clear_system_time_zone_cache();
     tzset();
 
     return current_time_zone;
diff --git a/Tests/LibUnicode/TestTimeZone.cpp b/Tests/LibUnicode/TestTimeZone.cpp
index 214b7ead4ae..208a0b90137 100644
--- a/Tests/LibUnicode/TestTimeZone.cpp
+++ b/Tests/LibUnicode/TestTimeZone.cpp
@@ -16,6 +16,7 @@ public:
         : m_time_zone(Core::Environment::get("TZ"sv))
     {
         MUST(Core::Environment::set("TZ"sv, time_zone, Core::Environment::Overwrite::Yes));
+        Unicode::clear_system_time_zone_cache();
     }
 
     ~TimeZoneGuard()
@@ -24,6 +25,7 @@ public:
             MUST(Core::Environment::set("TZ"sv, *m_time_zone, Core::Environment::Overwrite::Yes));
         else
             MUST(Core::Environment::unset("TZ"sv));
+        Unicode::clear_system_time_zone_cache();
     }
 
 private:
diff --git a/Userland/Libraries/LibUnicode/TimeZone.cpp b/Userland/Libraries/LibUnicode/TimeZone.cpp
index e6fdcb5c882..5b270ed3e84 100644
--- a/Userland/Libraries/LibUnicode/TimeZone.cpp
+++ b/Userland/Libraries/LibUnicode/TimeZone.cpp
@@ -15,8 +15,13 @@
 
 namespace Unicode {
 
-String current_time_zone()
+static Optional<String> cached_system_time_zone;
+
+String current_time_zone(UseTimeZoneCache)
 {
+    if (cached_system_time_zone.has_value())
+        return *cached_system_time_zone;
+
     UErrorCode status = U_ZERO_ERROR;
 
     auto time_zone = adopt_own_if_nonnull(icu::TimeZone::detectHostTimeZone());
@@ -32,7 +37,13 @@ String current_time_zone()
     if (icu_failure(status))
         return "UTC"_string;
 
-    return icu_string_to_string(time_zone_name);
+    cached_system_time_zone = icu_string_to_string(time_zone_name);
+    return *cached_system_time_zone;
+}
+
+void clear_system_time_zone_cache()
+{
+    cached_system_time_zone.clear();
 }
 
 // https://github.com/unicode-org/icu/blob/main/icu4c/source/tools/tzcode/icuzones
diff --git a/Userland/Libraries/LibUnicode/TimeZone.h b/Userland/Libraries/LibUnicode/TimeZone.h
index 41578b72705..2ccf036b43f 100644
--- a/Userland/Libraries/LibUnicode/TimeZone.h
+++ b/Userland/Libraries/LibUnicode/TimeZone.h
@@ -23,7 +23,13 @@ struct TimeZoneOffset {
     InDST in_dst { InDST::No };
 };
 
-String current_time_zone();
+enum class UseTimeZoneCache {
+    No,
+    Yes,
+};
+
+String current_time_zone(UseTimeZoneCache = UseTimeZoneCache::Yes);
+void clear_system_time_zone_cache();
 Vector<String> const& available_time_zones();
 Vector<String> available_time_zones_in_region(StringView region);
 Optional<String> resolve_primary_time_zone(StringView time_zone);