diff --git a/tools/check_prereq/Android.mk b/tools/check_prereq/Android.mk
new file mode 100644
index 0000000..abedff6
--- /dev/null
+++ b/tools/check_prereq/Android.mk
@@ -0,0 +1,30 @@
+# Copyright (C) 2009 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.
+
+LOCAL_PATH := $(call my-dir)
+include $(CLEAR_VARS)
+
+ifneq ($(TARGET_SIMULATOR),true)
+
+LOCAL_SRC_FILES := check_prereq.c
+LOCAL_MODULE := check_prereq
+LOCAL_FORCE_STATIC_EXECUTABLE := true
+LOCAL_MODULE_TAGS := eng
+LOCAL_C_INCLUDES +=
+LOCAL_STATIC_LIBRARIES += libcutils libc
+
+include $(BUILD_EXECUTABLE)
+
+endif  # !TARGET_SIMULATOR
+
diff --git a/tools/check_prereq/check_prereq.c b/tools/check_prereq/check_prereq.c
new file mode 100644
index 0000000..d7b8918
--- /dev/null
+++ b/tools/check_prereq/check_prereq.c
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2009 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 <stdio.h>
+#include <stdlib.h>
+#include <sys/system_properties.h>
+#include <cutils/properties.h>
+
+// Compare the timestamp of the new build (passed on the command line)
+// against the current value of ro.build.date.utc.  Exit successfully
+// if the new build is newer than the current build (or if the
+// timestamps are the same).
+int main(int argc, char** argv) {
+  if (argc != 2) {
+ usage:
+    fprintf(stderr, "usage: %s <timestamp>\n", argv[0]);
+    return 2;
+  }
+
+  char value[PROPERTY_VALUE_MAX];
+  char* default_value = "0";
+
+  property_get("ro.build.date.utc", value, default_value);
+
+  long current = strtol(value, NULL, 10);
+  char* end;
+  long install = strtol(argv[1], &end, 10);
+
+  printf("current build time: [%ld]  new build time: [%ld]\n",
+         current, install);
+
+  return (*end == 0 && current > 0 && install >= current) ? 0 : 1;
+}