diff --git a/core/main.mk b/core/main.mk
index 87bcd13..b290ce1 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -102,11 +102,8 @@
 # Write the build number to a file so it can be read back in
 # without changing the command line every time.  Avoids rebuilds
 # when using ninja.
-$(shell mkdir -p $(OUT_DIR) && \
-    echo -n $(BUILD_NUMBER) > $(OUT_DIR)/build_number.txt && \
-    echo -n "$(BUILD_DATETIME)" > $(OUT_DIR)/build_date.txt)
+$(shell mkdir -p $(OUT_DIR) && echo -n $(BUILD_NUMBER) > $(OUT_DIR)/build_number.txt)
 BUILD_NUMBER_FROM_FILE := $$(cat $(OUT_DIR)/build_number.txt)
-BUILD_DATETIME_FROM_FILE := $$(cat $(OUT_DIR)/build_date.txt)
 
 # CTS-specific config.
 -include cts/build/config.mk