diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0c6c566e8..db9e371aa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -135,7 +135,8 @@ else()
   endif()
 endif()
 
-string(TIMESTAMP GIT_DATE_TIME "%Y/%m/%d %H:%M:%S" UTC)
+string(TIMESTAMP TS "%Y/%m/%d %H:%M:%S" UTC)
+set(GIT_DATE_TIME "${TS}" CACHE STRING "the time we first built rocksdb")
 
 find_package(Git)