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;
+}