diff --git a/Makefile.am b/Makefile.am
index 6eb6157b..eb249792 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -24,7 +24,7 @@ BUILT_SOURCES = include/serno.h
 include/serno.h:
 	@if [ -d .git ]; then \
 		revh=`git log -1 --date=format:%Y%m%d --pretty=format:%cd-%h`; \
-		datecode=`git log -1 --date=format:%Y%m%d --pretty=format:%cd`; \
+		datecode=`git log -1 --pretty=format:%ct`; \
 		if [ -n "$$revh" ]; then \
 			echo '#define SERNO "'$$revh'"' >include/serno.h ; \
 			echo "#define DATECODE $${datecode}UL" >>include/serno.h; \