diff --git a/tests/time_test.cpp b/tests/time_test.cpp
new file mode 100644
index 0000000..9a5a706
--- /dev/null
+++ b/tests/time_test.cpp
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <sys/cdefs.h>
+#include <features.h>
+#include <gtest/gtest.h>
+
+#include <time.h>
+
+#ifdef __BIONIC__ // mktime_tz is a bionic extension.
+#include <libc/private/bionic_time.h>
+TEST(time, mktime_tz) {
+  struct tm epoch;
+  memset(&epoch, 0, sizeof(tm));
+  epoch.tm_year = 1970 - 1900;
+  epoch.tm_mon = 1;
+  epoch.tm_mday = 1;
+
+  // Alphabetically first. Coincidentally equivalent to UTC.
+  ASSERT_EQ(2678400, mktime_tz(&epoch, "Africa/Abidjan"));
+
+  // Alphabetically last. Coincidentally equivalent to UTC.
+  ASSERT_EQ(2678400, mktime_tz(&epoch, "Zulu"));
+
+  // Somewhere in the middle, not UTC.
+  ASSERT_EQ(2707200, mktime_tz(&epoch, "America/Los_Angeles"));
+
+  // Missing. Falls back to UTC.
+  ASSERT_EQ(2678400, mktime_tz(&epoch, "PST"));
+}
+#endif